The Pentagon [AFP=Yonhap News]

The headquarters of the U.S. Department of Defense (formerly the War Department), also known as the 'Pentagon', caused a stir on the 11th (local time) when it was temporarily closed due to a malfunction in its hazardous substance detection sensors.

In the morning, an evacuation alarm was issued after the Pentagon's internal air quality monitoring system detected the possibility of anthrax spores.

In response, the Department of Defense response team and fire authorities were dispatched, and a portion of the building was closed off for investigation.

Sources told CNN and the Washington Post (WP) that it is currently believed to be highly probable that the alarm was triggered by a malfunction in the detection sensor.

The Pentagon reportedly resumed normal operations in the afternoon after it was determined that there were no hazardous factors.