CHAMPAIGN, Ill. (AP) — The Illinois Environmental Protection Agency has finished its investigation into a September fish kill in a Sangamon River tributary and forwarded the case to the state attorney General's office.

Attorney General's office spokesman Scott Mulford told The News-Gazette newspaper in Champaign that the office received the case in October and is considering whether to take action.

About 40,000 fish and other animals died in a spill in Lone Tree Creek and a short stretch of the Sangamon below the point where the creek flows into the river. The location is about 15 miles northwest of Champaign.

The EPA hasn't revealed what was spilled. But the agency has indicated the likely pollution source is Stone Ridge Dairy, home to about 3,000 cows.

Copyright 2010 The Associated Press.