BRIDGEPORT — Firefighters battling a West Side house fire narrowly escaped death Thursday as the building exploded in a fireball.

Four firefighters crashed through the second-floor windows of the three-story Denver Avenue house as super-heated gases erupted in a "flashover."

The four — Lt. Michael Calderoni and Firefighters Tim Brickhouse, Steve Velasquez and Fernando Martins — landed on a lower roof and escaped serious injury. They were taken to Bridgeport Hospital to be treated for burns on their faces, heads and wrists. Also, firefighter Robert McNelis and another firefighter were reportedly hospitalized.

Assistant Chief Robert Petrucelli said later that he was waiting to determine the extent of their injuries. "I'm just grateful they got out in time," he said.

He said no other firefighters were injured and that no residents of the house were inside when the fire erupted about 3:30 p.m.

The yellow three-story house at 175-177 Denver Ave. was nearly a total loss, its left side consumed in a mass of black smoke and flame. Clouds of heavy smoke swirled around the densely built neighborhood.

Fifteen-year-old Angelica Casanova stood across the street, tears flowing down her face, as the blaze destroyed her home.

"Yes, that's where I used to live," she cried, pointing to the third floor. "Everything I own is there and it is all gone."

Her mother, Madeleine Casanova, gave her a hug. "I don't know what we are going to do; we don't even have a change of clothes."

Two families, including three children who lived in the house, were left homeless. They were expected to be relocated to temporary lodgings by the disaster relief team of the Southeastern Fairfield County Chapter of the American Red Cross.

John Cotter Jr., of Nutmeg Adjusters, said the building is owned by Henrietta Smith of Bridgeport and was insured. In the wake of the blaze, he was offering free smoke detectors to neighbors.

The fire "initially came in as a bedroom fire, but when firefighters arrived, the first and second floors were fully involved," Petrucelli said.

Flames were starting to lick the siding of a multi-family house next to the burning building, and the chief said firefighters were forced to redirect their attack to keep the fire from spreading.

Firefighters began crawling on their hands and knees through heavy black smoke to the burning home's second floor to ensure no one was inside. But the smoke suddenly ignited into a mass of flames.

The four firefighters managed to leap through the window seconds before the area was engulfed.

Petrucelli said the fire generated so much heat that a garage more than 20 feet behind the structure suddenly burst into flames and was a charred mass within seconds.

Heat from the fire was so intense that firefighters appeared to have sunburns. Afterward, they collapsed in the street, chugging bottles of water.

Petrucelli said it was too early to determine where the fire began and what caused it. The blaze remained under investigation late Thursday.

It was the second fire in the city's West Side in two days, following a blaze in a rooming house at State and Norman streets early Wednesday.

A resident, 62-year-old Alex Tzavaris, died in that fire and a second man was injured.

Petrucelli said the cause of that blaze is still being probed.

Daniel Tepfer, who covers state courts and law enforcement issues, can be reached at 330-6308.