Airport spokesman Troy Bell told the Richmond Times-Dispatch the facility received a phone call of a threatening nature soon after shortly after 6 a.m. EDT, and the terminal was cleared.
Virginia State Police Sgt. Thomas J. Molnar said the threat was determined to be credible, and federal, state and local law enforcement officers responded. Canine units assisted in a search of the airport terminal and the parking garages.
Bell said the terminal was reopened at about 9:25 a.m. EDT to airline workers. Public access would soon follow, he said.
"It's remarkably quiet and calm," traveler Trudi Allcott, an employee of medical supply company Owens & Minor Inc. who was flying to Los Angeles, told the Times-Dispatch. "I'd say everybody's being really patient."
At least 12 flights scheduled for departure were delayed and a smaller number of arrivals were delayed as well, the newspaper said.
Molnar said all flights were being held except for five flights permitted to land. They were held on the tarmac.