A security officer stands guard in front of the Pentagon in Arlington, Virginia, the United States, on June 11, 2026. Part of the Pentagon, the headquarters of the U.S. Department of Defense, was locked down and some areas were evacuated on Thursday due to an air quality issue detected inside the building, U.S. media reported. (Photo: Xinhua)

WASHINGTON, June 11 (Xinhua) -- Part of the Pentagon, the headquarters of the U.S. Department of Defense, was locked down and some areas were evacuated on Thursday due to an air quality issue detected inside the building, U.S. media reported.

Multiple floors and corridors inside the Pentagon were locked down while other areas were evacuated, CNN reported, citing three sources familiar with the situation.

Pentagon spokesman Sean Parnell said Thursday that systems inside the building had "detected an air quality issue necessitating precautionary measures until we determine its significance," according to CNN.

WTOP News, a Washington-area news outlet, along with other media sources, reported that the Pentagon was under a shelter-in-place order after systems detected an "air quality issue."

A post by Arlington County Fire & EMS on X said that units from the Arlington County Fire Department, including its Hazardous Materials Team, were operating at the Pentagon in support of the Pentagon Force Protection Agency's Hazmat Team during a "hazardous materials incident."