The Pentagon went into lockdown Thursday morning after internal monitoring systems detected what officials described as an air quality issue inside the building.
Multiple floors and corridors have been locked down and others are being evacuated. Both the Pentagon Force Protection Agency's hazmat response team and the Arlington County Fire Department's hazmat unit are on scene.
Pentagon spokesman Sean Parnell confirmed the situation around 11 AM Eastern. "Systems within the Pentagon have detected an air quality issue necessitating precautionary measures until we determine its significance," Parnell said. "The Department is executing standard protection protocols, including a shelter-in-place order for the affected area. Response teams are in place and ready to support building occupants."
Arlington Fire and EMS confirmed on social media that their hazmat unit is "currently operating at the Pentagon in support of PFPA's Hazmat Team during a hazardous materials incident."
CNN reporter Haley Britzky, who was inside the building when the incident began, reported that multiple floors and corridors were locked down while others were being evacuated, consistent with a response protocol designed to move people away from the affected area while containing the potential threat.
What triggered the air quality alert has not been disclosed. Whether any building occupants were injured or sickened has not been reported.
Whether the substance involved has been identified has not been confirmed. This is a developing situation and details are expected to emerge as hazmat teams complete their assessment.
The Pentagon is the headquarters of the United States Department of Defense and one of the most secure buildings in the country, housing approximately 23,000 military and civilian employees on any given workday.
A shelter-in-place order in the affected area means workers were instructed to remain where they are rather than evacuate, the appropriate protocol when the nature of a hazmat incident is unclear and evacuation through affected corridors could increase exposure risk.
No connection to any external threat has been confirmed. The Pentagon declined to characterize the incident beyond the air quality detection statement while response teams work to identify the cause.