The military base is the one where Barack Obama's presidential aircraft Air Force One is based.
US Joint Base Andrews near Washington was placed on lockdown because of reports of a gunman on the loose and personnel were told to shelter in place on Thursday. However, the base officials on Twitter said that there was no threat to the base.
Joint Base Andrews is the military facility where the US presidential aircraft, Air Force One, is based. President Barack Obama was not scheduled to use the base on Thursday.
The officials also said that "no notice" active shooter drill was scheduled on Thursday, however, there was "misidentification" of security forces.
"The incident is ongoing at the Malcolm Grow Medical Facility. First responders are on-scene now," base officials had said on Twitter. There were no immediate reports of gunfire or casualties.
On its Facebook page, Joint Base Andrews officials had said that the facility had been scheduled to conduct an active shooter exercise, "however, reports of a real-world active shooter situation were reported" at the medical facility.
"Due to the serious nature of this report, the base is reacting to ensure the safety of all personnel," it said. No other details were immediately available, and base officials did not return calls for comment. Prince George's County police directed questions to the base.
The US military has been on high alert for possible attacks at US locations after incidents such as the July 2015 shooting rampage that killed five service members at two military offices in Chattanooga, Tennessee, and the 2009 shooting at a US Army base in Fort Hood, Texas, in which a gunman killed 13 people.
Andrews base in Maryland is the primary military air installation in the Washington, DC, area, and is located about 15 miles (24 km) from the White House. Malcolm Grow is a full-service military hospital which according to its website is affiliated with the Uniformed Services University of Health Sciences and serves as a training facility for 48 medical residents and 31 health professionals.
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