JOINT BASE ANDREWS, Md. (AP) -- Officials say they have found no active shooter at Joint Base Andrews in Mayrland, despite initial reports that there was one.

The base was initially placed on lockdown, according to the base's Twitter account.

The Associated Press was reporting that Homeland Secretary Jeh Johnson said there was an "unfolding situation" at Andrews Air Force Base. Johnson is testifying before the Senate Judiciary Committee. He said he may have to take a break from the hearing as the situation at Andrews develops.

An employee at a medical facility at the base said an active-shooter drill had been planned, but officials later told workers it was a "real-world" situation. Rodney Smith is a patient advocate at the military post's medical facility. He said Thursday that he was on lockdown and didn't have any more information.

Smith said by phone: "First it was an active-shooter exercise. Then it came back 'real world."'

The base is the home of Air Force One, the aircraft that carries the President.

Emergency vehicles with lights on but no sirens could be seen on the base, according to the Associated Press.

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

Around 10:15 a.m., a few people could be seen walking out of the building, including a person being wheeled in a wheelchair.

Helicopters hovered overhead, but it is unclear if they are news or military helicopters.

Tweets from earlier today:

Reports are still coming in. Stay with WDRB News. We'll update this story as it develops.

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