The Latest: Biden trip delayed by base lockdown near DC

The vice president's office says he is waiting out the delay at his residence at the Naval Observatory in Washington.

The president, vice president and other senior government officials fly in and out of Joint Base Andrews.

Emergency vehicles with lights on but no sirens are in the area of a military base on lockdown after an active shooter was reported on the post.

At least three people in camouflage and helmets could be seen walking working dogs around the three-story medical building at Joint Base Andrews.

Joint Base Andrews, which is about 20 miles outside the nation's capital and is home to Air Force One, said in a tweet Thursday that the base is reacting to the active shooter report to ensure the safety of all personnel.

[...] Homeland Security Secretary Jeh Johnson says there is an "unfolding situation" at Joint Base Andrews in Maryland but is providing no further details.

Homeland Security Secretary Jeh Johnson says there is an "unfolding situation" at Joint Base Andrews in Maryland but is providing no further details.

An employee at a medical facility at Joint Base Andrews outside Washington says an active-shooter drill had been planned, but officials later told workers it was a "real-world" situation.