Joint Base Andrews in Maryland was placed on lockdown Thursday morning after someone mistakenly reported an active shooter during drill.

  • Joint Base Andrews was scheduled to conduct active-shooter exercise
  • Just before exercise, a real active-shooter report was called in
  • Officials say the 'active shooter' report was misunderstanding

No active shooter was found at the base located southeast outside Washington, D.C., in Prince George's County, law enforcement said.

The Air Force Base sent a tweet in the morning, instructing all personnel at the base to shelter in place.

The 'active shooter' call came in at about 9 a.m. after someone mistook an active shooter drill for the real thing, according to officials.

A safety drill was scheduled to be conducted on the base when an actual report of an active shooter was called in at Malcolm Grow medical facility. First responders are on the scene there.

Vice President Joe Biden's travel plans were delayed while the lockdown was in place. 

Just before 10:30 a.m., the all-clear was give at Joint Base Andrews and the lockdown was lifted.

Check back for updates.