CHICAGO - An erroneous report of an active shooter briefly shut down a US Air Force base on Thursday in the state of Ohio, before police gave the all-clear signal.

The false alarm was reported at 12:40 pm (1640 GMT) during a previously-scheduled training exercise at the Wright-Patterson Air Force Base.

Emergency crews responded to the scene of the call at the base hospital, and began a search to ensure no actual shooter was present, according to a statement released by the base.

The all-clear signal was sent out less than two hours later.

"This reported incident occurred during a normal, scheduled installation exercise which included an Active Shooter scenario," the base's statement said.

A member of the base security forces responding to the false alarm shot at a locked door in the hospital in order to open it during the security sweep, according to the statement. There were no other reports of shots fired.

It was unclear how the exercise was mistaken for a real-life emergency.

Eyewitness Elena Arrasmith, a member of the US military who works as an administrator on the base, told WHIO television that she and her colleagues were aware of the exercise.

"We were just aware that it was going on," she said. "The whole base is included in the training exercise."

Wright-Patterson is a key base for the US Air Force and headquarters to its Materiel Command, where new technologies are developed.