D.C. fire officials said yesterday that the lack of a sprinkler system may have been a factor in the spread of a spectacular fire that swept through the upper floors of the U.S. Postal Service Headquarters at L'Enfant Plaza, causing an estimated $100 million in damage and sending 25 firefighters to the hospital suffering from smoke inhalation and fatigue.

The four-alarm fire, described as one of the largest ever fought in the District, took 200 firefighters manning about 70 pieces of equipment about two hours to extinguish, officials said. They said the cause of the fire, which originated on the ninth floor Monday night, is still under investigation.

"If they had had sprinklers, it would not have been a major fire loss," said Assistant Fire Chief Maurice Kilby. Even though District fire codes do not require them in government buildings, he said, "we have always advocated sprinklers. They are proven to be a major fire deterrent."

About 2,700 Postal Service employes who work in the building were told not to report to work yesterday or today unless otherwise informed by their supervisors, according to Postal Service officials. They said there were about 20 postal employes in the building at the time of the fire.

Postmaster General William F. Bolger, who has offices in the building, said he did not know how long the employes will be displaced. He said emergency operations are being conducted from rooms at the L'Enfant Plaza Hotel, across from the Postal Service Headquarters, and there was no disruption in mail service.

"We are grateful that nobody was seriously hurt," Bolger said. "If we had to have a fire, I'm glad it was in the middle of the night when very few postal employes were on duty."

Fire department spokesman Ray Alfred said it probably will be at least a week or two before workers can return to offices in the building, which also houses the headquarters for the Public Broadcasting Service and offices for the General Accounting Office and the Smithsonian Institution.

PBS, which had about seven employes in the building at the time of the blaze, continued to broadcast by loading preprogrammed tapes into a computer system, according to Bruce Christensen, president of PBS.

Yesterday there were about four inches of water in the basement, where PBS houses tapes and electronic gear, but workers were able to get 48 hours of program tapes out of the building so the broadcast schedule could generally continue without disruption, he said.

The absence of a sprinkler system in the building prompted fire officials to express a long-standing complaint that too many buildings in the District do not have sprinklers, even though the city does not require them. The federally owned and operated Postal Service building does not by law have to comply with D.C. regulations anyway, fire officials said.

"There's one thing about sprinklers," said Kilby. "Right away they let you know that there's a fire. Then they help slow down the spread of the flame and contain it."

Ralph Stewart, a Postal Service spokesman, said the building "met fire safety regulations. It was not built with sprinklers and was not required to have sprinklers. We have security guards and regular inspections, so it was in sync with fire codes, both D.C. and federal."

According to Ted Leininger, the GSA's director of building services, there are 30 GSA-operated buildings in the District without sprinkler systems, including the State Department, the Department of Transportation, the J. Edgar Hoover building and the Commerce Department building. GSA has embarked on a seven-year, $98-million program to equip many of the buildings with sprinklers, he said.

"We don't feel the lack of sprinklers in any of these buildings is a life-safety problem," Leininger said. He said that GSA, the government's landlord, requires any building higher than six stories to have sprinklers. However, he said, GSA regulations do not apply to the Postal Service building.

Most of the fire damage from Monday night's blaze was confined to the top three floors, fire department spokesman Alfred said, but there was smoke and water damage to carpets, furniture, computers, ceilings and walls from the top floor of the 11-story, 600-foot-long building down to the basement.

"There is still water shooting out of cracks in the marble walls on the second floor," he said. "We don't know that some of those walls may come crashing down."

Fire officials did not give a breakdown of the $100 million damage estimate.

The fire was discovered about 11:20 p.m. Monday by a security guard who opened a door leading to the ninth floor and was met by a thick wall of smoke. Fire officials said that mounting an attack on the blaze was a tricky and challenging manuever, primarily because the heart of the blaze was nine floors above ground, it was intensely hot and noxious fumes were released from burning plastic.

Battalion Chief Robert Baker was the first fire chief at the scene. "I knew right away, from reports inside and outside in the rear of the building, that we had a big problem," Baker said.

About two minutes after his arrival, Baker called a second alarm and set up a command post on the eighth floor, directly below the fire, he said.

Firefighters carried 50-pound hoses, radio equipment and 30-pound air tanks to the command post, then attempted to make their way up the smoke-filled stairwell to the ninth floor, Baker said. Deputy Chief Howard Dixon called a third alarm.

"By the time they carried all that equipment up there, they were exhausted," Baker said. "Just to get up the stairwell and open the door to the ninth floor was like going into a 3,000-degree oven."

Battalion Chief Louis Carpenter, who was in charge of the eighth-floor command post, succumbed to the heat and smoke, and Deputy Chief Dixon went to relieve him and assess the situation, Baker said. Then Dixon, too, fell victim to exhaustion.

Outside, Fire Chief Theodore Coleman and Assistant Chief Kilby arrived and called a fourth alarm for extra manpower to relieve the stricken firefighters, Kilby said. According to Baker, air tanks were beginning to run low, and extra rescue squads and ambulance units were called to the scene.

From the back of the building, a lieutenant called Baker on the radio and told him the fire was rapidly progressing north, toward the firefighters, and that two windows had just blown out.

Unable to penetrate the blaze from the inside, firefighters backed off. Hoses were suspended from ladder trucks and trained water through windows.

It took about 15 minutes to get the firefighters to safety, Baker said. "When you spray 3,000 gallons per minute on a fire of that magnitude, the fire and smoke have no where to go but inside. If we have people in there, the heat and steam will burn them right up. I'm talking 100 percent burns."

When the fire was about 80 percent under control, Baker said, about 35 firefighters, with air tanks strapped to their backs, crawled along the floor to attack the pockets of fire that remained.

"It was totally disintegrated," Baker said of the ninth floor. "You couldn't even find the hallway. It was gone."

Last night, William Mould, president of the International Assciation of Firefighters Local 36, criticized an order by Fire Chief Theodore Coleman that Mould said reduced by one man the number of firefighters on each truck at the fire.

"I think that the more people you have, the less strain on individuals, and I don't think as many people would have needed to go to the hospital" if the rule had not been in force, Mould said.