BELFAST, Maine (AP) Residents near a burning potato-processing plant were urged to shelter in place on Thursday.

Firefighters were battling a massive fire at the Penobscot McCrum plant. There were no immediate reports of injuries.

Residents within a quarter-mile were told to shelter in place, and to close windows and turn off any ventilation systems that might draw in air from the outside, said Doug Nelson of the Waldo County Emergency Management Agency.

The plant had ammonia tanks that didn’t appear to be threatened by the fire but nonetheless were a concern for firefighters, he said.

At one point, the fire forced the closure of the U.S. Route 1 bridge. Belfast Area High School sent students home.