No hazardous material has been found after an initial investigation into an incident on Friday morning near the Pentagon, in which a man was detained with a suspicious vehicle, the FBI said.

In a statement, the FBI identified the man as Yonathan Melaku, 22, a resident of Alexandria, Virginia. He was initially observed inside the grounds of Arlington National Cemetery in the early morning hours, when the cemetery was closed.

Police detained and questioned him, and identified two potential public safety concerns, the FBI said. One was a backpack the man was carrying that contained unknown materials, and the other was a red 2011 Nissan vehicle found parked in a wooded area nearby the Pentagon, which police suspected the man may have been operating.

"Bomb experts at the scene, however, were able to determine that the items (in the backpack) were non-explosive and inert," the statement said, adding the materials will undergo further testing at the FBI Laboratory.

As for the suspicious vehicle, an initial search of it found no immediate threat, the FBI said. The vehicle was removed from the scene for further investigation.

The FBI also searched Melaku's residence in Alexandria and found nothing that may pose a serious threat.

"At this time, law enforcement believes Melaku acted alone and that there were no other locations or activity involved," the FBI said.

The FBI said Melaku joined the Marine Corps Reserve in 2007 and is currently listed as a Marine Corps reservist Lance Corporal.

The Washington Post reported on its website that during an interview at the scene, Melaku told authorities that he had bomb- making materials, including ammonium nitrate, in his backpack, but nothing harmful was found when bomb technicians ran a test at the scene.

Authorities found a notebook in the car, with the words "al- Qaeda," "Taliban" and "mujahideen" written inside, but there was no indication of any specific plot, according to the report.