One officer was injured in a shooting incident outside the National Security Agency (NSA), as the driver of a rented sports utility vehicle tried to enter a secured area, in Anne Arundel County, Maryland.
Two people were taken into federal custody after the incident, The Washington Post reported.
However, the authorities quickly concluded that the incident was not a terror attack.
An FBI spokesman said that one theory being investigated is whether the driver mistakenly turned onto a restricted parkway exit and panicked when he saw armed police.
"Until we complete all the interviews, we just can't say definitively," The Washington Post quoted the spokesman David Fitz as saying.
Other aspects of the inquiry are not yet known, including who fired the gunshots into the SUV's windshield and how the vehicle crashed.
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Gordon Johnson, the special agent in charge of the FBI's Baltimore field office, said that "preliminarily, gunfire was directed at the vehicle".
He, however, refused to comment whether any NSA police officers fired at the SUV.
Fitz said authorities ran the names of the three occupants of the SUV through databases and came up with no link to terrorism.
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