This story has been updated since it was originally published, and the number evacuated revised to 800.

FORT BRAGG, N.C. — Fort Bragg authorities were searching rooms Thursday in one of the largest buildings on the North Carolina Army post after safety alarms triggered an evacuation.

U.S. Army spokesman Paul Boyce said alarms were triggered around 1 p.m. Thursday in the building that houses U.S. Army Forces Command and U.S. Army Reserve Command. About 800 people were evacuated.

Boyce said the search by firefighters and law enforcement officers was launched as a precaution.

Normal operations resumed around 3:35 p.m. Thursday.

Firefighters and law enforcement officers searched each floor of the building before giving an all-clear. Boyce declined to say what triggered the alarm.

Boyce said some people who work in the building were sent home, but others who left car keys or other personal necessities are waiting in adjacent buildings.

The building houses uniformed and civilian workers with the two commands.