BELLFLOWER, Ill. (AP) — Investigators are trying to figure out exactly what caused a fish kill that destroyed 40,000 fish and other aquatic life in central Illinois.

The fish kill happened over nine miles of Lone Tree Creek and 1 mile of the Sangamon River, from the creek in southeastern McLean County to where it flows into the Sangamon.

A spokeswoman for the Illinois Environmental Protection Agency says the investigation is ongoing. But IEPA spokeswoman Maggie Carson tells the (Bloomington) Pantagraph that a nearby dairy is likely the source of contamination in the waterways. Carson says the dairy is cooperating with the investigation.

The Illinois Department of Natural Resources says the fish killed include large-and small-mouth bass, sunfish and carp. The DNR says mussels, frogs and crayfish were also killed.

Copyright 2010 The Associated Press.