Thousands of fish were killed in a 12-mile stretch of the Black River in Sanilac County, Mich. reports The manure washed into the river during heavy rains. Anglers started reporting dead fish on Monday.

Gary Towns, fisheries supervisor for the Department of Natural Resources in Southfield said it was the biggest fish kill he had ever seen. Some of the dead fish were 2 feet long and as much as 10 years old, according to Towns.

“We’re going to figure this out and hold whoever is responsible accountable,” said Bob McCann, spokesman for the Department of Environmental Quality.

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