WASHINGTON (AP) -- A fire, apparently caused by an electrical short, knocked out phone service in parts of the State Department on Wednesday and forced workers on two floors to evacuate the building after they locked up classified material.

The fire flared in a basement room near the 21st Street side of the building. Batteries that power some telephones were put out of commission, Richard Boucher, the State Department spokesman said.

The fire was confined to the basement and the damage did not appear to be widespread, he said. While fire engines responded, scores of evacuated waited outside for more than an hour until the fire was extinguished.

Fire Department spokesman Geoffrey Grambo said a cable that leads into a voltage room shorted, melting five large storage batteries used as a back up power source at the building.

Grambo says firefighters used sacks of concrete to prevent battery acid from spreading inside of the building. Workers and visitors had to be evacuated because of smoky conditions on the building's upper floors.

Grambo says there were no reported injuries.