Shots have been fired outside the headquarters of the National Security Agency, according to US media.
Three people were shot and a suspect was arrested in the incident outside America’s electronic espionage agency in Maryland, report local media.
Gunfire reportedly rang out after a black SUV pulled up at the entrance to the facility in Fort Meade.
An NSA spokesman was quoted as saying the situation was under control. Anne Arundel County police have responded.
CBS News images showed the vehicle with what appeared to be bullet holes in the front windscreen.
US President Donald Trump has been briefed on the incident, according to a White House spokeswoman.
In March 2015, one person was killed and another seriously wounded after driving a vehicle up to the NSA’s gate, ignoring commands to stop.
News reports later suggested the two occupants of the vehicle may have been under the influence of drugs after attending a party.