Officials at Fairmont Heights High School smelled smoke nearly three hours before they called firefighters to battle a blaze that caused $500,000 in damage to the school Jan. 4, Prince George's County fire officials said yesterday.

"Prompt notice could have kept the fire loss to one light fixture," declared Capt. William Goodwin, a fire department spokesman.

The fire reported at 4:20 p.m. after students had left for the day, destroyed the school's library and damaged its gymnasium. There was water damage to several classrooms. It took 125 firefighters about two hours to bring the two-alarm blaze under control. Four firefighters were injured and one is still hospitalized.

The school reopened for classes Jan. 8, following a weekend and the loss of one school day for students.

Release of the fire department's report on the blaze drew angry reactions from school officials yesterday.

"We still have not seen the report," said Brian Porter, a county school spokesman. "We are relying on the fire department to complete a blow by blow description of that fire, who first smelled that fire and who first reported it."

An informed source who refused to be identified said last night the school's librarian first reported smoke about 1:30 p.m., but it was concluded that it was dust swept up by workers who were cleaning air ducts.

At about 4:20 p.m., a school employe told night supervisor Al Craig there was smoke in the air. Craig then called the fire department.

The fire department originally said the fire apparently was caused by a faulty electrical transformer in a fluorescent light fixture in the library ceiling. The fire then spread to the gynmasium walls and ceiling.

School officials said most students had been sent home early on the day of the fire because of a snowstorm.

The loss, estimated by fire officials, included $400,000 damage to the school's structure and $100,000 damage to other school property. Besides the library books, rugs and furniture were destoryed.

Among the items destroyed was the school yearbook collection, dating to 1950, when the school opened. Several athletic trophies in the gynmasium melted, according to school officials.

One of the four firemen injured fighting the blaze, James R. Davis, 29, of the Capitol Heights Fire Department, is in fair condition at Prince George's General Hospital, where he was taken suffering from back injuries and smoke inhalation.