WASHINGTON (AP) _ The fire department in San Juan, Puerto Rico had too few men and inadequate equipment to effectively fight the Dec. 31 blaze at the Dpont Plaza Hotel that killed 96 people, a firefighters union said Friday.

''There was a dramatic lack of equipment to bring to bear on the fire and an equally dramatic lack of prepared manpower on the scene,'' said John A. Gannon, president of the International Association of Fire Fighters.

The union, which does not represent members of the San Juan fire department, sent a team to the Caribbean island after the New Year's Eve tragedy to interview firemen and study vdeotapes of the rescue effort.

''Fires bring out heroes and this one was no exception,'' Gannon told a news conference. ''However, effective firefighting should save lives, not risk them.''

Fewer than 60 on-duty firefighters were available for work when the 3:30 p.m. fire broke out, less than half the number that should have been on alert to tackle the job, Gannon said.

Moreover, he said, the union was told there were fewer than 20 pieces of breathing equipment - self-contained units like those used by scuba divers - on the scene. The Occupational Safety and Health Administration requires all firefighters entering a burning building to have such gear.

Some firemen reportedly told the union team they did not take time to don the proper protective clothing because they were in such a hurry to rescue those inside.

San Juan fire officials said they had enough tankers for the job, but they only produced one ladder truck with a 90-foot ladder, about 10 feet shorter and the longest ladder on the market, Gannon said.

But the aerial truck was of little use because the construction of the building prevented firemen from bringing the ladder close enough to rescue people from the 22-story tower. The lower levels stuck out, creating a barrier to the ladder, Gannon said.

But Rich Duffy, a technical specialist, said it is unclear whether the fire department could have done more to save people had it possessed better equipment and more people because the lower levels of the hotel were already ''fully involved'' by the time the fire trucks arrived on the scene.

It was obvious that the fire department, which took seven minutes to reach the scene, was not summoned early enough, Duffy said.

But the union does not know the time lag between when the fire was deliberately set in the lower level ballroom and when the fire department was notified, he said.

Murder and arson have been filed against two hotel workers accused of setting the fire in the hotel's lower-level ballroom. The workers are members of the Teamsters Union, which was deadlocked in a bitter contract dispute with the hotel management.

Most of the bodies were found in the mezzanine-level casino, one floor above the ballroom.

Gannon said his group has ''every indication from the investigators that a number of deaths and injuries involved not only fires, but the inhalation of highly poisonous gases and smokes.''

The union also criticized what it said was the refusal by Puerto Rican officials to allow military forensic specialists the right to examine the bodies to determine how the people died.

Elaine Henrion, an Army spokeswoman, said a three-member team from the Armed Forces Institute of Pathology flew to San Juan with investigators from the Bureau of Alcohol, Tobacco and Firearms.

The pathologists were sent in case island officials could not handle the workload of identifying bodies, she said, adding their services were not needed because Puerto Rican doctors said they had enough manpower. Pathologists from the FBI were called in to assist the local medical team.

Danny Velez, a spokesman for Gov. Rafael Hernandez Colon, said he had no information about the military forensics team.

Plastics in the hotel's furnishings may have contributed to the buildup of an incredible heat that caused a fireball, or flashover, in the casino, the officials said. Many synthetics have petroleum as a base and are highly flammable.

The union has lobbied for legislation, such as that in New York, which requires builders to test materials for toxicity before they are used.

Duffy said the union also backs legislation requiring buildings to install automatic sprinkler systems. Massachusetts recently passed such a law.

The Dupont Plaza, like 95 percent of the hotels in the United States, did not have a sprinkler system and Puerto Rico's code does not require them.

Union officials said they did not consider buildings in Puerto Rico unsafer than those in other parts of the country.

Immediately after the fire, Hernandez Colon pledged to revise the island's fire code. But he also said ''Puerto Rico has achieved one of the best fire- safety records in the United States.''