Officials are investigating a large fish die-off at a Great Bend lake.

The Great Bend Tribune reports thousands of dead fish have been reported at Veterans Memorial Lake.

Terry Hoff, acting Director of Public Lands for Great Bend, says crews have been cleaning up the fish as best they can, but it’s been tough to keep up. Hoff says the die-off killed most of the fish in the lake, from minnows to carp and bass.

Hoff says the city has contacted the Kansas Department of Health and Environment and the Kansas Department of Wildlife, Parks and Tourism to determine the cause.

The lake has been identified as experiencing a toxic blue-green algae bloom for the past several years, but algae hasn’t been named the cause of the kill.