The all clear has been given at Fort Lee Army base in Virginia after an active shooter was reported there.
Army officials said the base was on lockdown and personnel were told to enact active shooter protocols.
The four-story building involved is the headquarters for the Army's Combined Arms Support Command.
No other details were immediately available. The Department of Homeland Security uses the term "active shooter" to describe someone actively trying to kill people, usually in populated areas, with no pattern of choosing victims.
Fort Lee is about 200 kilometres from Washington and 40 kilometres south of the Virginia state capital, Richmond.
According to the military's website, Fort Lee is the Army's third-largest training site. Its daily population is 34,000, with service members, families, civilians and contractors.
