TOLEDO, Ohio (AP) – Ohio’s natural resources agency wants three people to pay more than $30,000 for three large fish kills that it says were caused by livestock manure spread on farm fields.

Investigators think ammonia-laden manure put onto the fields in northwestern Ohio ahead of rainstorms in August washed into creeks and caused the fish kills. An Ohio law put in place to combat algae in Lake Erie prohibits farmers from putting manure on fields before heavy rains because the manure also contains phosphorous that feeds algae.

Ohio officials say the manure spills killed close to 67,000 fish in Williams, Allen and Hardin counties. They say the biggest spill killed 37,000 fish near Delphos in August. The state says it could seek higher penalties if the three parties challenge the fines in court.