EATON, Ind. — Environmental investigators were trying to determine Monday whether someone intentionally caused a multimillion-gallon manure spill at an eastern Indiana hog farm.

The manure released Sunday from a lagoon at the defunct farm entered two drainage ditches and flowed to the Mississinewa River three miles away, causing a fish kill, said Amy Hartsock, a spokeswoman for the Indiana Department of Environmental Management.

Investigators from IDEM and the state Department of Natural Resources were on the scene Monday, trying to determine what caused the release of an estimated 4 million to 5 million gallons of manure.

Hartsock said investigators had found “a possible cut in the lagoon dike wall” that might have been deliberately made. The breach was repaired Sunday.

An IDEM contractor had been working since earlier this month to clean up excess manure at the farm, which went out of business after being prosecuted for violating environmental laws.

IDEM faces a possible bill of hundreds of thousands of dollars to have the manure shipped and treated at an Indianapolis sewage plant, although a spokesman said the agency is seeking payment from the property owners. Some of the manure might be spread on farmland, the spokesman said.

Muncie Sow Unit has pleaded guilty to a felony charge of failing to maintain its 12 million-gallon manure lagoon at a level to prevent overflows; sentencing is scheduled for June 3.