[Updated at 10:35 a.m.] Authorities closed commuter routes in the area around the Pentagon on Friday, snarling morning rush-hour traffic, after detaining a man acting suspiciously in Arlington National Cemetery and finding a car abandoned in bushes on the side of an area road.
No explosives or other suspicious material were found in the vehicle, a red 2011 Nissan, FBI Special Agent Brenda Heck told reporters. A backpack the detained man was carrying held bags of what Heck called a "non-explosive unknown material" that was being investigated, she said.
"There was not a device," said Heck, who specializes in counterterrorism but said her presence in the case was to represent the FBI in determining if any federal laws were violated.
Heck also said authorities believe the man, who was detained sometime after midnight, acted alone, and was thought to be in his mid-20s. She provided no further details of his identity or what he had told authorities.
Police shut down Route 27 between the cemetery and the Pentagon, as well as other roads in the area, causing major traffic jams. The security perimeter was part of the normal response to what Heck called suspicious activity, and she said roads would be reopened as soon as possible.
"From the FBI's perspective, it was just due diligence to protect this area," she said.
No charges have been filed against the detained man, said Heck, who emphasized the investigation was still in an early stage.
According to U.S. Park Police Sgt. David Schlosser, the detained man "wasn't forthcoming" about his identification or what he was doing in the national cemetery after midnight.
The security response was based on how authorities handle situations involving suspicious individuals or vehicles, Schlosser said. A Department of Homeland Security statement called the situation "a law enforcement matter at this time, with the U.S. Park Police and the Arlington County Police Department as leads and other federal agencies on the scene."