Pentagon building systems detected an air quality problem on Thursday morning. Part of the building was locked down as a result.

Workers on floors two through five were told to stay in place. Some staff were also moved out of the building.

Hazmat crews were sent in as a safety measure. Pentagon spokesman Sean Parnell confirmed the air quality issue.

He said precautionary steps were taken in response. A sensor had detected a possible anthrax presence.

Sources say it was a false alarm caused by a broken sensor. The shelter-in-place order stayed in effect while crews checked the problem.