False Alarm event in Virginia, Arlington, Pentagon Building area, United States of America on Thu 11th June 2026

The Pentagon was locked down and partially evacuated Thursday morning after a hazardous materials sensor triggered an alarm, prompting emergency response teams to sweep the building.

CNN, citing a source, said the sensor system detected the possible presence of anthrax. One source said the system was malfunctioning, resulting in a false alarm.

“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 post on X. 

After the alert, Parnell said the Pentagon executed standard protection protocols, including a shelter-in-place order for the affected area. “Response teams are in place and ready to support building occupants,” he added.

Fire and hazmat teams from Virginia responded to the incident, according to reports.

At 1:31 p.m., Parnell said subsequent testing confirmed no hazard exists and that normal operations have resumed. 

“We express our sincere appreciation to the first responders for their swift actions to ensure the safety of all personnel,” Parnell added.