The DEC was called to the village of Perry sewage treatment plant Saturday.
Heavy rain and snow melt led to a discharge of an estimated 90,000 gallons of untreated sewage into the Silver Lake Outlet.
DEC investigators say the leak probably lasted about six hours, and was over when they arrived.
The DEC reports evidence of tiny grease particles in the Water Street Road area, but is unsure if and how much damage occurred.
The DEC says the Perry plant didn't have the capacity to handle the extra water.