Washington DC’s Metropolitan Police Department told CNN they were responding to the incident but there was no further information regarding the exact nature of the man with the gun.
According to the US Navy, the facility is under a shelter-in-place order. Police responded to a report about a man with a gun in the facility.
Police and ambulance vehicles surrounded the Washington Navy Yard on Thursday morning.
The facility is the site where in 2013 a gunman killed 12 people.