Security was stepped up at U.S. government buildings in the nation’s capital on Thursday after the Washington Navy Yard was shut down while authorities investigated initial reports of an active shooter, Bloomberg reported.

The military installation was under “lockdown/shelter in place,” the U.S. Navy said in a tweet Thursday morning. “Investigation continues. No further info at this time.”

There was no confirmation from the Navy or law enforcement authorities of a shooting, a suspect or any injuries.

The Navy Yard was the site of a mass shooting in 2013, when contractor Aaron Alexis killed a dozen people.