Army officials say the base is on lockdown and personnel have been 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 25 miles south of Richmond and about 130 miles from Washington. 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.