Pentagon smoke incident contained

An aerial view of the Pentagon building, June 15, 2005. The Pentagon was partially evacuated on Friday morning due to heavy smoke near a construction area in the main concourse of the Department of Defense headquarters, officials said.

WASHINGTON (Reuters) - Part of the Pentagon was evacuated on Friday due to heavy smoke from a small fire in a utility room, but no injuries were reported and the building's main concourse was reopened within hours.

A small section on the fifth floor of the Defense Department headquarters building remained closed as Pentagon and Arlington County, Virginia, firefighters investigated.

But the building entrance near the Pentagon's Metro transit stop was reopened.

A Pentagon spokeswoman said insulation caught fire in a utility room on the fifth floor in the outermost ring of the building, known as the "E Ring."

"There was insulation that burned. It was what caused most of the smoke," she said.

But the problem was contained and employees were allowed to re-enter the building. Only sections of two corridors on the fifth floor remained closed.

The Pentagon is one of the world's largest office buildings, so big that the U.S. capitol building could fit inside any one of its five wedge-shaped sections. More than 20,000 people, both military and civilian, work inside.

(Reporting by Kristin Roberts, editing by Patricia Zengerle)