MOREHEAD CITY, N.C. — Officials shut down a North Carolina port and urged people to leave the area today after a forklift operator punctured at least one container filled with a powerful explosive.

The material was pentaerythritol tetranitrate, but it's not clear what form it was in, Mayor Jerry Jones said.

The chemical is also known as PETN, the substance authorities say was part of a device a Nigerian man used to try to bring down a Detroit-bound Northwest flight on Christmas Day. PETN is often used in military explosives and found inside blasting caps. It is also the primary ingredient in detonating cords used for industrial explosions.

Jones said the damage appeared to be an accident and there were no concerns about terrorism. He said a dock worker punctured a container as he was unloading barrels of the chemical.

Any accident involving hazardous materials must be reported immediately to the Morehead City Fire Department.

"That's how we found out about it," he said. "We don't think there's a danger. Everything is under control. But you have to be careful."

Officials had earlier said nine containers were punctured, but Jones said he was not sure exactly how many were damaged.

He said he did not know the chemical was being shipped through the port, but whoever was shipping it should have contacted the city's emergency management department.