UPDATE: (AP) A law enforcement official says no active shooter was found at a military post outside Washington.

The law enforcement official was not authorized to discuss the matter by name and spoke on condition of anonymity.

JOINT BASE ANDREWS, Md. (AP) — Homeland Secretary Jeh Johnson says an unspecified security incident is taking place Joint Base Andrews outside Washington.

Joint Base Andrews tweets that the base is on lockdown due to a report of an active shooter. This is where Air Force 1 is housed.

The tweet sent Thursday morning instructs all personnel at the base in Washington's Maryland suburbs to shelter in place and says more information will be released as it comes.

A second tweet from the base says the incident is ongoing at the Malcolm Grow Medical Facility and first responders are on the scene. It instructs everyone to continue to shelter in place, a precaution meant to keep people safe while remaining indoors.

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Joint Base Andrews tweet
Joint Base Andrews Tweets