US military's Joint Base Andrews on Thursday sent out an "All Clear"message hours after a lockdown was enforced because of reports that an active shooter was on the premises, The base authorities had announced on Twitter that the incident took place at the Malcolm Grow Medical Facility.

According to AP, a law enforcement official said no active shooter has been found.

Soon after the reports surfaced, the administration tweeted the first respondents had reached the scene and all personnel had been ordered to shelter in place. "The base was scheduled to conduct an active shooter exercise, however, reports of a real-world active shooter situation were reported," the official Twitter handle of JBA said.

The airbase hosts two Boeing Aircraft that are called Air Force One when President Barack Obama uses them for his official trips.