EXHIBIT 21.1 SUBSIDIARIES OF THE REGISTRANT.
U.S. SUBSIDIARIES
Name of Subsidiaries State of Organization Trade Names
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Penn Wilson CNG, Inc. Delaware None
Penn CNG Holdings, Inc. Delaware None
FOREIGN SUBSIDIARIES
Name of Subsidiaries Country of Organization Trade Names
----------------------------------- ----------------------- -----------
PennWill, S.A. de C.V. Mexico None
Camiones Ecologicos, S.A. de C.V. Mexico None
Grupo Ecologico Industrial, S.A. de C.V. Mexico None
Estacion Ambiental, S.A. de C.V. Mexico None
Estacion Ambiental II, S.A. de C.V. Mexico None
Serinc, S.A. de C.V. Mexico None
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