DUPLIN COUNTY, N.C. — Inspectors with the State Department of Labor are investigating an ammonia leak in Duplin County that forced the evacuation of the

House of Raeford

poultry plant, nearby residences and closed a school early Tuesday morning.

Officials say a valve broke around 5:30 a.m. at the plant located on Highway 117 near the town of Rose Hill.

Ten thousand pounds of ammonia was released and emergency crews say a vapor cloud formed over the building. The leak was contained around 8:45 a.m.

Two hundred fifty employees at the plant were evacuated. About 20 employees were taken to area hospitals for treatment of minor respiratory problems, including coughing and sore throats.

"When the atmosphere is that rich in ammonia, it can actually cause death," Duplin County Fire Marshal Jimmy Pate said.

When winds started to shift the vapor cloud away from the plant, emergency workers closed nearby Rose Hill-Magnolia Elementary School.

They also asked about 100 people living in the area to leave their homes. Those residents were able to return home by 9 a.m.

"Our communications system started getting calls that people were smelling ammonia in their residences and as they were going to work," Pate said.

The valve has been fixed and ammonia has been cleared from the building. Labor officials will determine whether House of Raeford should be fined.