WASHINGTON (CNN) - Parts of the Pentagon were under lockdown Thursday after officials detected an air quality issue inside the building.

A shelter-in-place order was issued for the affected area. Multiple sources described the situation as a hazardous materials incident.

Officials said multiple floors and corridors inside the Pentagon were locked down while other areas were being evacuated.

Police were reportedly seen inside the building wearing gas masks and full chemical protective gear.

There was no word on what may have triggered the incident.

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