VILLAGE OF DARIEN, Wis. (AP) — Authorities say 15 people were taken to hospitals after an ammonia leak at a Birds Eye food plant in southeastern Wisconsin.

Multiple agencies responded early Sunday to the plant in the Village of Darien.

Authorities say 140 people were working overnight at the factory when alarms and sensors started going off. Ammonia is used at the facility for the freezing and cooling of food.

A hazardous materials team official says 15 people were taken to five area hospitals. New Jersey-based Pinnacle Foods, which owns Birds Eye, said Sunday night that most have been released, while three people remain under observation.

Seventy-five workers were checked at the scene and released. The Janesville Gazette reports authorities suspect a "mechanical malfunction" led to the leak.

Officials say there is no threat to the community.