Joint Base Andrews in Maryland, the military facility in suburban Washington where the presidential aircraft Air Force One is based, was put on lockdown on Thursday, the base said, and ABC News reported a woman claiming to have a bomb appeared at the visitors center.

The base said on Twitter that at roughly 5:15 p.m. there was "a security incident" reported at the Visitor Control Center on base, and that emergency responders were on scene.

"The Main Gate is currently in lockdown. All personnel and residents should avoid the area until further notice," a base official Tweeted.

(Reporting by Eric Beech; Editing by Eric Walsh and James Dalgleish)