A spectacular three-alarm fire early this morning heavily damaged the controversial 14-story Olmsted Building being constructed atop Arlington's Clarendon Metro station and sent firefighters fleeing for cover as burning timbers and red-hot reinforcement bars rained down on adjacent streets.

The blaze, which was first reported shortly before 1 a.m., quickly involved a massive complex of wooden and steel concrete structural forms on the top three floors and burned furiously for nearly an hour before it was brought under control about 2:15 a.m.

At one point, firefighters stationed on Highland Street and Washington Boulevard were forced to drop their hoses and flee as the metal bars burst from the building like fireworks.

A ladder truck, unable to get closer than a block from the fire, trained its spray on the debris that fell atop the parking garage and concourse that spread out from the building's central tower.

The Olmsted Building, which at 200 feet towers over surrounding structures and exceeds the normal height restrictions by more than 60 feet, was bitterly opposed by neighborhood residents. It was approved for construction at Highland Street and Wilson and Washington boulevards only after developers convinced the County Board that the building would serve as the focus of the area.

"When you have a building under construction," said Arlington Fire Chief Thomas Hawkins, "It's like fighting a lumberyard fire 11 stories in the air. It ain't a picnic. I wouldn't want to estimate the damage."

A total of 10 engine companies -- almost the county's entire firefighting force -- along with equipment from Fairfax County and Alexandria fought the blaze. Fire officials said heaviest damage appeared to be on the Washington Boulevard side, where the granite facade on the upper floors was detroyed.

As the fire burned out of control sparks and other debris fell as far as three blocks away and drifted into the entrances of the Clarendon Metro station.

The blaze was finally brought under control after the driver of a ladder truck was able to work the vehicle alongside the building on Highland Street, and firefighters extended the ladder fully and trained water on the blazing timbers burning on several floors.

Other firefighters were then able to enter the seventh floor of the building and begin beating their way toward the blazing top floors. At the height of the fire firefighters had difficulty getting water to the upper floors and firemen manning hoses atop ladders and on the floors below the blaze issued desperate calls for more pressure. Minutes later, as collapse of the top stories seemed imminent, official on the streets below ordered the men to drop their hoses and seek cover.

The plans for the gigantic, multimillion-dollar building, first proposed in January 1982, brought protest even from the federal National Capital Planning Commission, which said the vista from the U.S. Capitol to Arlington ridge would be destroyed by the structure.

The commission's criticism, rare for a private building, surprised architects who defended their design, which called for another floor and a height of more than 220 feet.