The Pentagon resumed normal operations on Thursday after issuing a shelter-in-place order amid reports of hazardous materials.
"Earlier this morning, Pentagon occupants were notified of a potential air quality issue, prompting immediate precautionary safety measures and evaluation," Pentagon spokesman Sean Parnell said in a statement. "Subsequent testing confirmed no hazard exists, and normal operations have resumed."
Mr Parnell had said earlier that the Pentagon's "sophisticated system" had detected a problem prompting "precautionary measures" that included a shelter-in-place order.
“Response teams are in place and ready to support building occupants,” he said.
Firefighters were investigating the incident, Arlington County fire and rescue officials said in a post on X. Emergency responders on the scene were reportedly wearing full gas masks and chemical protection suits.
Floors two to five were reportedly locked down, as well as some corridors.
The five-sided Pentagon building, hit during the September 11, 2001, Al Qaeda attacks, is one of the world's largest office buildings.
