McLEAN, Va. (AP) _ A fire at CIA headquarters Tuesday caused more than $1 million in damage, authorities said.

Investigators from the Fairfax County Fire Department determined the fire began after slag, melted by a welder's torch, fell onto some wooden shelves in a utility room on the fifth floor of the older headquarters building on the closed CIA campus outside of Washington.

The building, and the nearby new headquarters building, were evacuated after fire alarms sounded around 5:50 p.m. EDT Tuesday.

During the fire, CIA uniformed security officers escorted the local firefighters through the building. Ten of those officers were treated for smoke inhalation at the scene.

Two more CIA employees were hospitalized for smoke inhalation and later released. Some CIA employees were given Wednesday off because of the heavy smoke in the building, but all are expected back at work Thursday.

A CIA spokesman, Mark Mansfield, said the fire didn't reach any sensitive areas in the building. The spokesman said that regular agency briefings to policy-makers were conducted on schedule Wednesday.