A smoky, two-alarm fire forced evacuation of CIA headquarters in Langley late yesterday, and the agency's 24-hour operations center suspended activity, a CIA spokesman said.

Ten uniformed agency security officers were treated at the scene for smoke inhalation, and two other CIA employees were taken to a hospital, authorities said. They were said to be in good condition.

The fire was discovered about 5:45 p.m. in the northeast section of what is known as the original headquarters building. An adjacent building is known as the new headquarters.

A CIA spokesman said only essential employees in the original headquarters should report to work today. He said they should go to the new building.

The cause of the fire was not immediately known. Mike Reilly, a spokesman for the Fairfax County Fire Department, said that it broke out in an area that included vents, trash chutes and electrical vaults and that "dozens of CIA personnel were evacuated."

CIA public affairs chief Bill Harlow said the agency's operations center -- its "eyes and ears" -- asked counterparts elsewhere in the government to assume its responsibilities temporarily. The center returned to service at an alternative site within two hours, he said.