A three-alarm fire caused extensive damage to a Harvard office building at 4-10 Story St. in Harvard Square late yesterday afternoon.

No one was hurt in the fire, the cause of which had still not been determined last night. Approximately 150 people work in the building--home to the Radcliffe development office and the Harvard AIDS Institute--but it was unknown how many were still inside when the fire started at about 4:45 p.m.

Three Cambridge fire trucks responded to the scene, and firefighters had to break through third-floor windows to gain access to the building.

There was serious smoke damage to the fourth and fifth floors, as well as smoke and water damage to the first, second and third floors. The building, which houses the Charles Webb furniture showroom on its street level, has about 50,000 sq. ft. of office and retail space.

Tenants of the building, which is owned by Harvard Planning and Real Estate, will meet early today to discuss the impact of the fire and to make alternate arrangements for office space, said Harvard spokesperson Joe Wrinn.

Wrinn said workers had been on the vacant third floor, formerly occupied by an artists' collaborative, yesterday morning to move furniture.

Firefighters were able to contain the flames on the third floor, which is about 1500 sq. ft., Wrinn said.

Last night, Harvard police still had Story St. blocked off, and the strong odor of smoke could be smelled as far way as the Harvard Square pit.

Story St. itself was littered with shattered glass and detritus thrown from the building during the fire.

Harvard's Office of Cultural Survival and several Extension School offices are also housed in the less-damaged lower floors of the building.