Three people were shot and wounded near the US National Security Agency's headquarters in Maryland, and one person was in custody, local media reported on Wednesday.
The Federal Bureau of Investigation sent agents to investigate the incident, its Baltimore office said on Twitter.
CBS News broadcast images of a black sport utility vehicle parked near the entrance of the NSA with what appeared to be bullet holes in the front windshield. The vehicle was at the end of a dead-end lane marked by concrete NSA-stamped barricade blocks on one side and a chain-link fence on the other, near a toll-booth-style entrance gate, the CBS video showed.
Local fire and police departments said on Twitter they were responding to a possible shooting incident outside the agency's campus in Fort Meade.
A spokesman at Fort Meade, about 48km northeast of Washington, said he could not confirm that a shooting has occurred or that a vehicle was at the gate. He did confirm that one person had been injured and transported, although he did not say where the person had been transported to. He also confirmed that Highway 32 around Fort Meade has been closed
A White House spokeswoman said President Donald Trump had been briefed on the incident.
In March 2015, two people tried to drive their sports utility vehicle through the NSA's heavily guarded gate. Officers shot at the vehicle when they refused to stop, killing one of the occupants. The people in the vehicle may have taken a wrong turn after partying and taking drugs, according to news reports.