At least three people were hospitalized this morning after an unauthorized car approached the gates of the National Security Agency in Fort Meade, Maryland, leading to a car crash and gunfire, according to FBI officials.

Several details of the incident are still murky, but aerial footage showed a black SUV with airbags deployed, apparently after crashing into concrete barriers. According to FBI investigators, three people in the car pulled into the NSA complex. An NSA police officer, a civilian “onlooker,” and one person in the car were hospitalized in an incident that followed, although none appeared to be injured by gunfire. All three people riding in the car have been detained.

At a press conference, an FBI official said investigators had reached the “preliminary” conclusion that the vehicle was fired at by law enforcement, but could not rule out whether other weapons were involved. The FBI stressed that there was no indication the incident was related to terrorism.

The NSA said in a tweet that “the situation is under control and there’s no ongoing security or safety threat.” The agency has not responded to a request for more information.

The FBI’s Baltimore office said in a tweet that the incident was “contained.”

The incident is not the first shooting at the NSA complex. In 2015, one person was left dead, and two were injured, in another incident at the the agency’s Fort Meade gates.