Joint Base Anacostia-Bolling in Washington, D.C., issued a safety advisory Thursday after the discovery of a "suspicious package."
Officials say the package was discovered outside Building 412, which prompted an evacuation. Authorities then set up a 1,000-foot perimeter and asked for personnel to avoid the area.
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Several other buildings are under a "shelter in place" order as authorities continue to assess the situation, WUSA 9 reported.
An ordinance team has deployed to the scene.
The base similarly entered a lockdown a few weeks ago when a "potentially armed person" appeared on the grounds, FOX 5 DC reported.
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Police determined the man had fled the scene of a shooting, and he was promptly taken into custody.
This is a developing story.