SC 13D/A 1 e15068sc13d.txt SCHEDULE 13D/A UNITED STATES SECURITIES AND EXHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13D Under the Securities Exchange Act of 1934 (Amendment No. 36)* TUBOS DE ACERO DE MEXICO, S.A. -------------------------------------------------------------------------------- (Name of Issuer) Common Stock -------------------------------------------------------------------------------- (Title of Class of Securities) 898592506 -------------------------------------------------------------------------------- (CUSIP Number) Mr. Fernando R. Mantilla Av. Leandro N. Alem 1067, 28th Floor, 1001 - Buenos Aires, Argentina (54-11) 4018-2245 -------------------------------------------------------------------------------- (Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications) June 10, 2003 -------------------------------------------------------------------------------- (Date of Event which Requires Filing of this Statement) If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of ss.ss.240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. |_| Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See ss.240.13d-7 for other parties to whom copies are to be sent. *The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page. The information required on the remainder of this cover page shall not bee deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). CUSIP No. 898592506 -------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). SIDERCA Sociedad Anonima Industrial y Comercial -------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a)....................................................................... (b)....................................................................... -------------------------------------------------------------------------------- 3. SEC Use Only ............................................................. -------------------------------------------------------------------------------- 4. Source of Funds (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 5. Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ............................................................. -------------------------------------------------------------------------------- 6. Citizenship or Place of Organization ARGENTINA -------------------------------------------------------------------------------- Number of Shares 7. Sole Voting Power NONE Beneficially --------------------------------------------------------- Owned by 8. Shared Voting Power: 324,064,223 Shares of TAMSA Each Reporting Common Stock (1 ADR=5 shares) Person With --------------------------------------------------------- 9. Sole Dispositive Power NONE --------------------------------------------------------- 10. Shared Dispositive Power 324,064,223 Shares of TAMSA Common Stock (1 ADR=5 shares) -------------------------------------------------------------------------------- 11. Aggregate Amount Beneficially Owned by Each Reporting Person 324,064,223 -------------------------------------------------------------------------------- 12. Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 13. Percent of Class Represented by Amount in Row (11) 94.50% -------------------------------------------------------------------------------- 14. Type of Reporting Person (See Instructions) CO .......................................................................... .......................................................................... .......................................................................... .......................................................................... .......................................................................... CUSIP No. 898592506 -------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). SIDERCA INTERNATIONAL ApS -------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a) ...................................................................... (b) ...................................................................... -------------------------------------------------------------------------------- 3. SEC Use Only ............................................................. -------------------------------------------------------------------------------- 4. Source of Funds (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 5. Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ............................................................. -------------------------------------------------------------------------------- 6. Citizenship or Place of Organization DENMARK -------------------------------------------------------------------------------- Number of Shares 7. Sole Voting Power NONE Beneficially Owned by --------------------------------------------------------- Each Reporting 8. Shared Voting Power 324,064,223 Shares of TAMSA Person With Common Stock (1 ADR=5 shares) --------------------------------------------------------- 9. Sole Dispositive Power NONE --------------------------------------------------------- 10. Shared Dispositive Power 324,064,223 Shares of TAMSA Common Stock (1 ADR=5 shares) -------------------------------------------------------------------------------- 11. Aggregate Amount Beneficially Owned by Each Reporting Person 324,064,223 -------------------------------------------------------------------------------- 12. Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 13. Percent of Class Represented by Amount in Row (11) 94.50% -------------------------------------------------------------------------------- 14. Type of Reporting Person (See Instructions) CO .......................................................................... .......................................................................... .......................................................................... .......................................................................... .......................................................................... CUSIP No. 898592506 -------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). ROCCA & PARTNERS Sociedad Anonima -------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a)....................................................................... (b)....................................................................... -------------------------------------------------------------------------------- 3. SEC Use Only ............................................................. -------------------------------------------------------------------------------- 4. Source of Funds (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 5. Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ............................................................. -------------------------------------------------------------------------------- 6. Citizenship or Place of Organization BRITISH VIRGIN ISLANDS -------------------------------------------------------------------------------- Number of Shares 7. Sole Voting Power NONE Beneficially Owned by --------------------------------------------------------- Each Reporting 8. Shared Voting Power 324,064,223 Shares of TAMSA Person With Common Stock (1 ADR=5 shares) --------------------------------------------------------- 9. Sole Dispositive Power NONE --------------------------------------------------------- 10. Shared Dispositive Power 324,064,223 Shares of TAMSA Common Stock (1 ADR=5 shares) -------------------------------------------------------------------------------- 11. Aggregate Amount Beneficially Owned by Each Reporting Person 324,064,223 -------------------------------------------------------------------------------- 12. Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 13. Percent of Class Represented by Amount in Row (11) 94.50% -------------------------------------------------------------------------------- 14. Type of Reporting Person (See Instructions) CO .......................................................................... .......................................................................... .......................................................................... .......................................................................... .......................................................................... CUSIP No. 898592506 -------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). SAN FAUSTIN N.V. -------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a)....................................................................... (b)....................................................................... -------------------------------------------------------------------------------- 3. SEC Use Only ............................................................. -------------------------------------------------------------------------------- 4. Source of Funds (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 5. Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ............................................................. -------------------------------------------------------------------------------- 6. Citizenship or Place of Organization NETHERLANDS ANTILLES -------------------------------------------------------------------------------- Number of Shares 7. Sole Voting Power NONE Beneficially Owned by --------------------------------------------------------- Each Reporting 8. Shared Voting Power 324,064,223 Shares of TAMSA Person With Common Stock (1 ADR=5 shares) --------------------------------------------------------- 9. Sole Dispositive Power NONE --------------------------------------------------------- 10. Shared Dispositive Power 324,064,223 Shares of TAMSA Common Stock (1 ADR=5 shares) -------------------------------------------------------------------------------- 11. Aggregate Amount Beneficially Owned by Each Reporting Person 324,064,223 -------------------------------------------------------------------------------- 12. Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 13. Percent of Class Represented by Amount in Row (11) 94.50% -------------------------------------------------------------------------------- 14. Type of Reporting Person (See Instructions) CO ........................................................................... ........................................................................... ........................................................................... ........................................................................... ........................................................................... CUSIP No. 898592506 -------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). SIDERTUBES S.A. -------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a)....................................................................... (b)....................................................................... -------------------------------------------------------------------------------- 3. SEC Use Only ............................................................. -------------------------------------------------------------------------------- 4. Source of Funds (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 5. Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ............................................................. -------------------------------------------------------------------------------- 6. Citizenship or Place of Organization LUXEMBOURG -------------------------------------------------------------------------------- Number of Shares 7. Sole Voting Power NONE Beneficially Owned by --------------------------------------------------------- Each Reporting 8. Shared Voting Power 324,064,223 Shares of TAMSA Person With Common Stock (1 ADR=5 shares) --------------------------------------------------------- 9. Sole Dispositive Power NONE --------------------------------------------------------- 10. Shared Dispositive Power 324,064,223 Shares of TAMSA Common Stock (1 ADR=5 shares) -------------------------------------------------------------------------------- 11. Aggregate Amount Beneficially Owned by Each Reporting Person 324,064,223 -------------------------------------------------------------------------------- 12. Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 13. Percent of Class Represented by Amount in Row (11) 94.50% -------------------------------------------------------------------------------- 14. Type of Reporting Person (See Instructions) CO .......................................................................... .......................................................................... .......................................................................... .......................................................................... .......................................................................... CUSIP No. 898592506 -------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). I.I.I. INDUSTRIAL INVESTMENTS INC. -------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a)....................................................................... (b)....................................................................... -------------------------------------------------------------------------------- 3. SEC Use Only ............................................................. -------------------------------------------------------------------------------- 4. Source of Funds (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 5. Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ............................................................. -------------------------------------------------------------------------------- 6. Citizenship or Place of Organization BRITISH VIRGIN ISLANDS -------------------------------------------------------------------------------- Number of Shares 7. Sole Voting Power NONE Beneficially Owned by --------------------------------------------------------- Each Reporting 8. Shared Voting Power 324,064,223 Shares of TAMSA Person With Common Stock (1 ADR=5 shares) --------------------------------------------------------- 9. Sole Dispositive Power NONE --------------------------------------------------------- 10. Shared Dispositive Power 324,064,223 Shares of TAMSA Common Stock (1 ADR=5 shares) -------------------------------------------------------------------------------- 11. Aggregate Amount Beneficially Owned by Each Reporting Person 324,064,223 -------------------------------------------------------------------------------- 12. Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 13. Percent of Class Represented by Amount in Row (11) 94.50% -------------------------------------------------------------------------------- 14. Type of Reporting Person (See Instructions) CO .......................................................................... .......................................................................... .......................................................................... .......................................................................... .......................................................................... CUSIP No. 898592506 -------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). TENARIS S.A. -------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a)....................................................................... (b)....................................................................... -------------------------------------------------------------------------------- 3. SEC Use Only ............................................................. -------------------------------------------------------------------------------- 4. Source of Funds (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 5. Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ............................................................. -------------------------------------------------------------------------------- 6. Citizenship or Place of Organization LUXEMBOURG -------------------------------------------------------------------------------- Number of Shares 7. Sole Voting Power NONE Beneficially Owned by --------------------------------------------------------- Each Reporting 8. Shared Voting Power 324,064,223 Shares of TAMSA Person With Common Stock (1 ADR=5 shares) --------------------------------------------------------- 9. Sole Dispositive Power NONE --------------------------------------------------------- 10. Shared Dispositive Power 324,064,223 Shares of TAMSA Common Stock (1 ADR=5 shares) -------------------------------------------------------------------------------- 11. Aggregate Amount Beneficially Owned by Each Reporting Person 324,064,223 -------------------------------------------------------------------------------- 12. Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 13. Percent of Class Represented by Amount in Row (11) 94.50% -------------------------------------------------------------------------------- 14. Type of Reporting Person (See Instructions) CO .......................................................................... .......................................................................... .......................................................................... .......................................................................... .......................................................................... CUSIP No. 898592506 -------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). INVERTUB S.A. -------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a)....................................................................... (b)....................................................................... -------------------------------------------------------------------------------- 3. SEC Use Only ............................................................. -------------------------------------------------------------------------------- 4. Source of Funds (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 5. Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ............................................................. -------------------------------------------------------------------------------- 6. Citizenship or Place of Organization ARGENTINA -------------------------------------------------------------------------------- Number of Shares 7. Sole Voting Power NONE Beneficially Owned by --------------------------------------------------------- Each Reporting 8. Shared Voting Power 324,064,223 Shares of TAMSA Person With Common Stock (1 ADR=5 shares) --------------------------------------------------------- 9. Sole Dispositive Power NONE --------------------------------------------------------- 10. Shared Dispositive Power 324,064,223 Shares of TAMSA Common Stock (1 ADR=5 shares) -------------------------------------------------------------------------------- 11. Aggregate Amount Beneficially Owned by Each Reporting Person 324,064,223 -------------------------------------------------------------------------------- 12. Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 13. Percent of Class Represented by Amount in Row (11) 94.50% -------------------------------------------------------------------------------- 14. Type of Reporting Person (See Instructions) CO .......................................................................... .......................................................................... .......................................................................... .......................................................................... .......................................................................... CUSIP No. 898592506 -------------------------------------------------------------------------------- 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). SIDTAM LIMITED -------------------------------------------------------------------------------- 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a)....................................................................... (b)....................................................................... -------------------------------------------------------------------------------- 3. SEC Use Only ............................................................. -------------------------------------------------------------------------------- 4. Source of Funds (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 5. Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ............................................................. -------------------------------------------------------------------------------- 6. Citizenship or Place of Organization BRITISH VIRGIN ISLANDS -------------------------------------------------------------------------------- Number of Shares 7. Sole Voting Power NONE Beneficially Owned by --------------------------------------------------------- Each Reporting 8. Shared Voting Power 324,064,223 Shares of TAMSA Person With Common Stock (1 ADR=5 shares) --------------------------------------------------------- 9. Sole Dispositive Power NONE --------------------------------------------------------- 10. Shared Dispositive Power 324,064,223 Shares of TAMSA Common Stock (1 ADR=5 shares) -------------------------------------------------------------------------------- 11. Aggregate Amount Beneficially Owned by Each Reporting Person 324,064,223 -------------------------------------------------------------------------------- 12. Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) NOT APPLICABLE -------------------------------------------------------------------------------- 13. Percent of Class Represented by Amount in Row (11) 94.50% -------------------------------------------------------------------------------- 14. Type of Reporting Person (See Instructions) CO .......................................................................... .......................................................................... .......................................................................... .......................................................................... .......................................................................... AMENDMENT No. 37 TO SCHEDULE 13D This Amendment No. 36 amends the Statement on Schedule 13D originally filed on September 24, 1992 and amended and restated as of November 11, 2002, as amended ("Schedule 13D"), on behalf of Siderca Sociedad Anonima, Industrial y Comercial ("Siderca SAIC"), and Siderca International ApS ("Siderca ApS"), together with Rocca & Partners S.A. ("Rocca & Partners"), San Faustin N.V. ("San Faustin"), Sidertubes S.A. ("Sidertubes"), I.I.I. Industrial Investments Inc. ("III BVI"), Tenaris S.A. ("Tenaris"), Invertub Sociedad Anonima ("Invertub") and Sidtam Limited ("Sidtam") (collectively, "Reporting Persons"), relating to the common shares, without par value (the "TAMSA Shares"), of Tubos de Acero de Mexico, S.A., a Mexican company ("TAMSA"). Item 2. Identity and Background No changes except the following: On June 10, 2003, Mr. Roberto Rocca passed away and therefore he is no longer a reporting person. An updated list of the directors and executive officers of Siderca S.A.I.C., Rocca & Partners S.A., San Faustin N.V., Sidertubes S.A., I.I.I. Industrial Investments Inc. and Tenaris S.A., and the information required by subparagraphs (a) through (c) and subparagraph (f) of Item 2 of Schedule 13D, is set forth respectively on Schedules A through F and is hereby incorporated herein by reference. None of the Reporting Persons, and to their best knowledge, none of the executive officers or directors of Siderca S.A.I.C., Rocca & Partners S.A., San Faustin N.V., Sidertubes S.A., I.I.I. Industrial Investments Inc. and Tenaris S.A. has during the last five years been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation to such laws. Item 5. Interest in Securities of the Issuer No changes. Item 7. Material to be Filed as Exhibits Powers of attorney for Tenaris S.A., I.I.I. Industrial Investments Inc. and Invertub S.A. are incorporated by reference into this Amendment to the ones filed as exhibits to Amendment No. 34 to the Schedule 13D. Powers of attorney for each of the other Reporting Persons are incorporated by reference into this Amendment to the ones filed as exhibits to Amendment No. 23 to the Schedule 13D of Siderca ApS. The written agreement of the Reporting Persons related to the filing of this Schedule 13D as required by Rule 13d-k(1)(iii) is included in the signature pages hereto and is hereby filed as an exhibit hereto. Schedule A Siderca S.A.I.C.

---------------------------------------------------------------------------------------------------------- Ruben Fidalgo Av. Leandro Alem 1067, Domestic Sales Manager Argentine Domestic Sales Manager Buenos Aires - Argentina of Siderca ---------------------------------------------------------------------------------------------------------- Juan Carlos Bongartz Av. Leandro Alem 1067, Industrial Relations Argentine Industrial Relations Buenos Aires - Argentina Manager of Siderca Manager ---------------------------------------------------------------------------------------------------------- Guillermo Murphy Av. Leandro Alem 1067, Planning Manager of Argentine Planning Manager Buenos Aires - Argentina Siderca ----------------------------------------------------------------------------------------------------------

Schedule B Rocca & Partners S.A.

Schedule C San Faustin N.V.

Schedule D I.I.I. Industrial Investments Inc.

Schedule E Sidertubes S.A.

Schedule F Tenaris S.A.

---------------------------------------------------------------------------------------------------------- Guillermo F. Vogel Edificio Parque Reforma, Vice Chairman of Tamsa Mexican Campos Eliseos 400, 11560 and Vice-President Mexico, D.F., Mexico Finance of Tenaris ----------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------ Ricardo Soler Av. Dr. Gastao Vidigal Neto Managing Director of Welded Argentine Managing Director of Welded 475 Pipe Operations of Tenaris Pipe Operations Barrio Cidade Nova 12440-900 Pindamonhangaba Sao Paulo, Brazil ------------------------------------------------------------------------------------------------------------------ Cecilia Bilesio Corporate Edificio Parque Reforma, Corporate Secretary of Argentine Secretary Campos Eliseos 400, 11560 Tenaris Mexico, D.F., Mexico ------------------------------------------------------------------------------------------------------------------

SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by ROCCA & PARTNERS S.A. to sign this statement, certify that the information set forth in this Schedule 13D is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13D on his own behalf and on behalf of SAN FAUSTIN N.V., SIDERCA Sociedad Anonima Industrial y Comercial, SIDERCA INTERNATIONAL ApS, SIDERTUBES S.A., I.I.I. INDUSTRIAL INVESTMENTS Inc., TENARIS S.A., INVERTUB Sociedad Anonima and SIDTAM LIMITED. June 17, 2003 /s/ Fernando Mantilla ---------------------- Fernando Mantilla Attorney-in-fact SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by SAN FAUSTIN N.V. to sign this statement, certify that the information set forth in this Schedule 13D is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13D on his own behalf and on behalf of ROCCA & PARTNERS S.A., SIDERCA Sociedad Anonima Industrial y Comercial, SIDERCA INTERNATIONAL ApS, SIDERTUBES S.A., I.I.I. INDUSTRIAL INVESTMENTS Inc., TENARIS S.A., INVERTUB Sociedad Anonima and SIDTAM LIMITED. June 17, 2003 /s/ Fernando Mantilla ---------------------- Fernando Mantilla Attorney-in-fact SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by I.I.I. INDUSTRIAL INVESTMENTS Inc. to sign this statement, certify that the information set forth in this Schedule 13D is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13D on his own behalf and on behalf of ROCCA & PARTNERS S.A., SAN FAUSTIN N.V., SIDERCA Sociedad Anonima Industrial y Comercial, SIDERCA INTERNATIONAL ApS, SIDERTUBES S.A., TENARIS S.A., INVERTUB Sociedad Anonima and SIDTAM LIMITED. June 17, 2003 /s/ Fernando Mantilla ---------------------- Fernando Mantilla Attorney-in-fact SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by SIDERTUBES S.A. to sign this statement, certify that the information set forth in this Schedule 13D is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13D on his own behalf and on behalf of ROCCA & PARTNERS S.A., SAN FAUSTIN N.V., SIDERCA Sociedad Anonima Industrial y Comercial, SIDERCA INTERNATIONAL ApS, I.I.I. INDUSTRIAL INVESTMENTS Inc., INVERTUB Sociedad Anonima, TENARIS S.A. and SIDTAM LIMITED. June 17, 2003 /s/ Fernando Mantilla ---------------------- Fernando Mantilla Attorney-in-fact SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by TENARIS S.A. to sign this statement, certify that the information set forth in this Schedule 13D is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13D on his own behalf and on behalf of ROCCA & PARTNERS S.A., SAN FAUSTIN N.V., SIDERCA Sociedad Anonima Industrial y Comercial, SIDERCA INTERNATIONAL ApS, SIDERTUBES S.A., I.I.I. INDUSTRIAL INVESTMENTS Inc., INVERTUB Sociedad Anonima and SIDTAM LIMITED. June 17, 2003 /s/ Fernando Mantilla ---------------------- Fernando Mantilla Attorney-in-fact SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by INVERTUB S.A. to sign this statement, certify that the information set forth in this Schedule 13D is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13D on his own behalf and on behalf of ROCCA & PARTNERS S.A., SAN FAUSTIN N.V., SIDERCA Sociedad Anonima Industrial y Comercial, SIDERCA INTERNATIONAL ApS, SIDERTUBES S.A., I.I.I. INDUSTRIAL INVESTMENTS Inc., TENARIS S.A. and SIDTAM LIMITED. June 17, 2003 /s/ Fernando Mantilla ---------------------- Fernando Mantilla Attorney-in-fact SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by SIDERCA SOCIEDAD ANONIMA INDUSTRIAL Y COMERCIAL to sign this statement, certify that the information set forth in this Schedule 13D is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13D on his own behalf and on behalf of ROCCA & PARTNERS S.A., SAN FAUSTIN N.V., SIDERCA INTERNATIONAL ApS, SIDERTUBES S.A., I.I.I. INDUSTRIAL INVESTMENTS Inc., TENARIS S.A., INVERTUB S.A. and SIDTAM LIMITED. June 17, 2003 /s/ Fernando Mantilla ---------------------- Fernando Mantilla Attorney-in-fact SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by SIDERCA INTERNATIONAL ApS to sign this statement, certify that the information set forth in this Schedule 13D is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13D on his own behalf and on behalf of ROCCA & PARTNERS S.A., SAN FAUSTIN N.V., SIDERCA Sociedad Anonima Industrial y Comercial, SIDERTUBES S.A., I.I.I. INDUSTRIAL INVESTMENTS Inc., TENARIS S.A., INVERTUB Sociedad Anonima and SIDTAM LIMITED. June 17, 2003 /s/ Fernando Mantilla ---------------------- Fernando Mantilla Attorney-in-fact SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I, Fernando Mantilla, attorney duly authorized by SIDTAM LIMITED to sign this statement, certify that the information set forth in this Schedule 13D is true, complete and correct. Pursuant to Rule 13d-1(k)(1), the undersigned joins in the filing of this Schedule 13D on his own behalf and on behalf of ROCCA & PARTNERS S.A., SAN FAUSTIN N.V., SIDERCA Sociedad Anonima Industrial y Comercial, SIDERCA INTERNATIONAL ApS, I.I.I. INDUSTRIAL INVESTMENTS Inc., TENARIS S.A. INVERTUB Sociedad Anonima and SIDERTUBES S.A. June 17, 2003 /s/ Fernando Mantilla ---------------------- Fernando Mantilla Attorney-in-fact Exhibit index: 99.1 Powers of attorney (incorporated by reference to Amendments No. 23 and 34) 99.2 Written agreement of the Reporting Persons (included in signature pages)

TUBES OF STEEL OF MEXICO SA SC 13D/A