1 person in custody in investigation at Pentagon

Pentagon police spokesman Chris Layman said the car was in bushes near the Pentagon's north parking lot.

Associated PressLaw enforcement work near the Pentagon after a suspicious vehicle forced multiple road closures Friday, June 17, 2011 in Arlington, Va. Officials in Washington say one man is under arrest after they found his car, parked in the bushes near the Pentagon, contained material that appears to be ammonium nitrate. The vehicle also contained spent 9 mm shells and written materials stating "al Qaeda Taliban rules."

ARLINGTON, Va. — One person was taken into custody early Friday after being found near the Pentagon with suspicious materials in his backpack, authorities said.

The man, who is in his 20s, was detained after he was found after hours inside Arlington National Cemetery and was initially uncooperative, authorities said. Officers searched his nearby car, a red 2011 Nissan, but found nothing suspicious inside, said Brenda Heck, special agent in charge of the counterterrorism unit of the FBI's Washington field office.

The man, whose name was not released, was being detained but had not been charged as of Friday morning, officials said. Heck said officials believe the man acted alone.

She said the man was carrying a backpack with suspicious items, and a non-explosive material was found.

A law enforcement official speaking on the condition of anonymity said officials found what appeared to be an unknown quantity of ammonium nitrate. The official, who was not authorized to release the information, said nothing else was found that would have enabled an explosion. The official said tests were being done to determine the substance and the exact concentration.

Ammonium nitrate is a chemical compound that is widely used in fertilizers and can be used in explosives with the correct concentration.

Pentagon police spokesman Chris Layman said the car was in bushes near the Pentagon's north parking lot.

In another incident earlier this week, a motorist found with a gun and what appeared to be a suspicious package near the Pentagon was taken into custody.