SUBSIDIARIES OF REGISTRANT Exhibit 21 Percentage of Voting Securities Owned by Registrant Canadian-Montana Gas Company Limited An Alberta Corporation 100 Canadian-Montana Pipe Line Company An Alberta Corporation 100 Glacier Gas Company A Montana Corporation 100 Colstrip Community Services Company A Montana Corporation 100 Continental Energy Services, Inc. A Montana Corporation 100 EMPECO, Inc. A Montana Corporation (A wholly-owned subsidiary of Continental Energy Services, Inc.) 100 EMPECO II, Inc. A Montana Corporation (A wholly-owned subsidiary of Continental Energy Services, Inc.) 100 EMPECO III, Inc. A Montana Corporation (A wholly-owned subsidiary of Continental Energy Services, Inc.) 100 EMPECO IV, Inc. A Montana Corporation (A wholly-owned subsidiary of Continental Energy Services, Inc.) 100 EMPECO V, Inc. A Montana Corporation (A wholly-owned subsidiary of Continental Energy Services, Inc.) 100 EMPECO VI - TE, Inc. A Montana Corporation (A wholly-owned subsidiary of Continental Energy Services, Inc.) 100 SUBSIDIARIES OF REGISTRANT Exhibit 21 Percentage of Voting Securities Owned by Registrant North American Energy Services Company A Washington Corporation (A wholly-owned subsidiary of Continental Energy Services, Inc.) 100 Engineering Design & Associates A Washington Corporation (A wholly-owned subsidiary of North American Energy Services Company) 100 North American Contract Employee Services A Washington Corporation (A wholly-owned subsidiary of North American Energy Services Company) 100 ECI Holdings, Ltd. Investment in English Partnership in a Gas-fired Cogeneration Project (A 47.5% owned subsidiary of Continental Energy Services, Inc.) 50 Entech, Inc. A Montana Corporation 100 Western Energy Company A Montana Corporation 100 Western Syncoal Company A Montana Corporation (A wholly-owned subsidiary of Western Energy Company) 100 Montana Participacoes, Ltda. A Brazilian Corporation (A wholly-owned subsidiary of Western Energy Company) 100 Financiera Ulkea Sociedad Anonima (SA) A Uruguayan Corporation (A wholly-owned subsidiary of Montana Participacoes, Ltda.) 100 SUBSIDIARIES OF REGISTRANT Exhibit 21 Percentage of Voting Securities Owned by Registrant Northwestern Resources Co. A Montana Corporation 100 Altana Exploration Company A Montana Corporation 100 Altana Exploration (UK) Limited A United Kingdom Corporation (A wholly-owned subsidiary of Altana Exploration Company) 100 Intercontinental Energy Corporation A Texas Corporation (A wholly-owned subsidiary of Altana Exploration Company) 100 Entech Altamont, Inc. A Montana Corporation 100 Roan Resources, Ltd. An Alberta Corporation 100 North American Resources Company A Montana Corporation 100 Nortech Energy Corp. A Texas Corporation 50 Tetragenics Company A Montana Corporation 100 TRI Touch America, Inc. A Montana Corporation 100 Basin Resources, Inc. A Colorado Corporation 100 Horizon Coal Services, Inc. A Montana Corporation 100 SUBSIDIARIES OF REGISTRANT Exhibit 21 Percentage of Voting Securities Owned by Registrant North Central Energy Company A Colorado Corporation 100 Trinidad Railway, Inc. A Montana Corporation 100 Note: The above listed companies are included in the Consolidated Financial Statements of the registrant.