A precautionary evacuation of several nearby residents took place, Fulton Fire Department Acting Chief Paul Foster said.
The leak was reported about 8:22 p.m. Chief Foster said the leak occurred in a 1 1/4 inch return pipe of the refrigeration system and was located, isolated and contained by on-site maintenance.
The Oswego County Hazardous Materials Team, the Oswego County Health Department and the State Department of Environmental Conservation Spill Response also responded to the scene with the Fulton Fire Department.
As a precaution, residents in the area of Jerome and Gansvoort streets in Fulton were evacuated. The Oswego County E-911 Communications Center and Fulton Police Department notified nearby residents.
Foster said any ammonia remaining in the surrounding atmosphere may be an irritant to residents and those experiencing any irritation may wish not to stay at home tonight.
Displaced residents may go to the War Memorial or the Community Room at the Fulton Municipal Building.
The plant is owned by Pinnacle Foods.