A Marine Corps reservist carrying a backpack containing what initially appeared to be bomb-making material was detained near the Pentagon early Friday, but authorities later said the suspicious items were not explosive.
Yonathan Melaku, 22, of Alexandria, Va., was discovered after 1 a.m. Friday inside Arlington National Cemetery, several hours after it had closed.
As officials investigated the contents of Melaku's bag and his car parked nearby, roads were closed around the Pentagon, snarling rush hour traffic for hours.
Melaku, a naturalized citizen originally from Ethiopia, was detained for trespassing after becoming uncooperative, authorities said, but hadn't been charged as of Friday night.
Melaku was not believed to have any ties to al-Qaida or any other terrorist organization, according to a law enforcement official who spoke on the condition of anonymity.
Melaku had a bag with a substance that at least initially was feared to be ammonium nitrate, which can be used in explosives with the correct concentration and is also widely used in fertilizers, according to a second law enforcement official. But the official said there was nothing in Melaku's possession that could have detonated or caused an explosion.
Both officials spoke on the condition of anonymity because they were not authorized to talk about the investigation.
The FBI declined to specify what was in the backpack, but said the items were undergoing further testing at the laboratory in Quantico and that Melaku did not possess any explosives. It was not immediately clear late Friday what any testing showed.
"I can tell you this was not a device and that the products in the backpack are inert," said Brenda Heck, special agent in charge of the counterterrorism unit at the FBI's Washington field office.
Melaku joined the Marine Corps Reserves in September 2007 and is currently listed as a lance corporal and motor vehicle operator with a combat engineer battalion headquartered in Baltimore, according to the FBI. He has received the National Defense Service Medal and the Selected Marine Corps Reserve Medal. He has not been deployed overseas.
Lt. Col. Francis Piccoli, a spokesman for the Marine Forces Reserve, said Melaku was not on active duty at the time he was detained. He said a quick review of his records showed nothing negative in his background or performance.
Melaku remained in the custody of the U.S. Park Police as investigators in protective white suits and bomb-sniffing dogs went through his brick town-home in suburban Washington.
Melaku was arrested a few weeks ago in Leesburg, Va., accused of damaging cars and stealing items from them. His attorney in that case did not return a call seeking comment Friday.
In another incident earlier this week that officials treated as suspicious, a vehicle was pulled over near the Pentagon after the driver appeared to be backing up against traffic. Authorities determined that people inside the vehicle were taking pictures of the Pentagon, and an occupant admitted carrying a gun, said Pentagon police spokesman Chris Layman. The incidents appeared unrelated, he said.
Sullivan reported from Washington. Associated Press writers Adam Goldman, Matthew Barakat, Karen Mahabir, Lolita Baldor and Jessica Gresko contributed to this report.