The Pentagon lifted a shelter-in-place order Thursday afternoon after building safety systems detected what officials described as an air quality issue that prompted an emergency response involving hazardous materials teams.

Pentagon chief spokesman Sean Parnell said in a statement that occupants were notified of the potential air quality issue Thursday morning, which triggered "immediate precautionary safety measures and evaluation." Multiple floors of the building were locked down for several hours as a precaution.

Hazardous materials crews were deployed to investigate the incident and conduct air testing throughout the affected areas of the building. The response followed standard safety protocols when building systems detect potential environmental concerns.

Sources later indicated the incident was likely a false alarm, with no actual hazardous materials present. Air testing confirmed that no hazard existed in the building, according to officials.

The Pentagon returned to normal operations Thursday afternoon after the all-clear was issued. The incident temporarily disrupted work at the headquarters of the U.S. Department of Defense, though officials emphasized the response was precautionary in nature.