An early-morning fire roared through a stable with a broken sprinkler system at Belmont Park today, killing at least 45 thoroughbred racehorses, including 36 under the care of John Campo, one of the nation's best-known trainers.

Initial estimates placed the value of the lost horses and the barn at up to $10 million, a Nassau County police spokesman said. However, track officials said in a statement later the barn was worth $1 million and the horses were valued at up to $5 million.

The fire apparently was accidental.

Two horses were rescued. One was Pleasant Sea, an offspring of Pleasant Colony, the 1981 Kentucky Derby and Preakness winner. Other Pleasant Colony progeny were believed to have died in the blaze, authorities said. The horses all died of smoke inhalation, according to Elmont Fire Chief James Snadecky.

Concessions, an unraced 3-year-old, was named by its trainer Bobby Ribaudo as one of those killed. NYRA officials were checking lip brands in an attempt to identify the horses, but said they may not have a complete list until Monday morning.

The green one-story structure that caught fire contained a hayloft, and Keenan and other officials said it was possible the hay caught fire spontaneously. The fire was reported at 1:19 a.m. and took more than 200 firefighters more than an hour to contain. Two of them suffered minor injuries, were treated at a local hospital and released.

The cause of the fire remained undetermined late today, and authorities found "nothing that indicates it would be suspicious," said Detective Lt. William Gutersloh, commanding officer of the Nassau County arson squad.

Arson investigators were sifting through rubble, looking for clues and interviewing employes and others, Gutersloh said. Owners indicated "a good portion of the horses were not insured, and they will have substantial losses," he said.

Belmont has been closed for the season since Oct. 22. Horses stabled there have been running at Aqueduct this winter.

John Keenan, a vice president of the New York Racing Association, said the sprinkler system did not work because its pipes burst late last week when temperatures zoomed from near zero to almost 50 degrees in one day.

"The sprinklers had to be drained and would have been repaired today or tomorrow," he said.

Flames shot 50 feet high and caused a large section of the 400-foot-long barn to cave in, Snadecky said. Most of the horses suffocated in their 12-foot-by-12-foot stalls where they had been tied up for the night, said John Loser, assistant fire chief.

"It looked like a fireball in the middle of the barn," Loser said. "It was tough to make a decision not to charge in there and try to get the horses out."

"They didn't have a chance," said Gene Martello, a trainer who works with horses in a neighboring barn.

The fire broke out in Barn 48 on the grounds of the nation's largest track. It was first spotted by the night watchman, who "from one end saw flames coming out of a stall in the middle," Keenan said.

The horses were among more than 2,000 kept in 64 barns on the grounds of the 430-acre complex.

Trainer Mike Daggett was near tears as he described how eight horses he trained died in the fire.

"I love these horses. I'm so sorry they had to go -- and go that way," said Daggett, who has worked with horses since graduation from Portland State University.

"Money doesn't mean anything to me," he said. "By being with them every day, every month, every year, you see them fulfilled at the race track by winning. That's how they become a part of you."

Horse owner Robert Kern said he lost three, including one he had bought just hours before the fire.

"I'm sick," he said. "I'm very upset and disturbed and brokenhearted. It's a terrible tragedy."

The fire department knew of the sprinkler problem and barn security had been beefed up, Keenan said.

Although some of the horses might have been able to break out of their stalls, Keenan said that would have been unusual.

"The nature of a horse is he considers that stable his home, and if something happens, he's more inclined to go into it than out," he said.