ALBERT CITY, Iowa (AP) — State environmental officials says a hog farm manure tank leak was the likely cause of a fish kill in a northwestern Iowa tributary this week. The Iowa Department of Natural Resources says the leak happened over the weekend near Albert City when an unknown amount of manure was released into the tributary.

On Sunday, the DNR found a some dead fish, manure and elevated ammonia levels throughout four miles of the tributary, which connects to the North Raccoon River. The incident was reported by farm owner Kris Ehlers, who suspected a failed valve on the manure tank. DNR workers concluded the spill did come from Ehlers’ farm, but was likely coming through underground tile lines.