A partially-blocked sewer main on the east end of Main Street in Niles led to a leak of sewer discharge into the St. Joseph River Wednesday.

Assistant Public Works Director Joe Ray said about 750 gallons leaked into the river.

The DPW discovered the leak at 1 p.m. and less than one hour later, the blocked main was fixed and the river cleaned.

“The sewer on the west side of the river goes under the river,” Ray said. “There was an accumulation of grease and silt in the manhole, so it wouldn’t let it flow through.”

Ray said water at residents’ homes should not be affected.

“There should be no backups or anything,” he said.

The city’s National Pollutant Discharge Elimination System permit requires notification to the Michigan Department of Environmental Quality, the Berrien County Health Department and the city’s newspaper.