MATTOON, Ill. (AP) — Reports of fish dying in Lake Mattoon have drawn a response from the Illinois Department of Natural Resources.

Agency spokesman Chris Young tells the Journal Gazette and Times-Courier in Mattoon that the fish kill seems to be caused by a virus specific to carp.

Department staff visited the lake after fishermen reported seeing dead carp, starting around Memorial Day. Dead fish could still be seen Thursday afternoon along the shoreline.

Lake Supervisor Joel Pittman says it’s the biggest fish kill he’s seen in his 20 years working at the lake.

Pittman says the fish kill seems to have run its course. Most of the dead carp he’s found recently appear to have died several days ago.