The US Department of Defense has given the all-clear after fire crews were called to the Pentagon building over a possible air quality problem.
Follow-up tests found there was no danger, a spokesman wrote on the platform X on Thursday, adding that normal operations had resumed.
Earlier, people inside the headquarters of the US Department of Defense had been told to remain at their workstations.
Systems had indicated a problem with air quality, according to the spokesman.
The fire service in Arlington, Virginia, across the Potomac River from Washington, had been called to the building to provide support, including hazardous materials experts.
