An aerial view of a shooting scene at the National Security Agency at Fort Meade in Maryland is pictured in this still image take from video, March 30, 2015. [Photo/cfp]

WASHINGTON - Two people tried to run their vehicle through National Security Agency's entrance gates near Washington on Monday before guards shot one of them dead, and the vehicle's second occupant and a police officer were injured, officials said.

The two, who were dressed in women's clothes and may be transgender, tried to drive their sport utility vehicle through an entrance gate at the spy agency's Fort Meade, Maryland, headquarters, a senior US official said.

Their motive was not immediately known but officials said there was no evidence the incident was linked to terrorism. One official said investigators were looking into whether drugs were involved.

The two people in a vehicle "attempted an unauthorized entry at a National Security Agency gate," the NSA said in a statement. The pair failed to follow a police officer's directions to leave the gate area and barriers were put up.