In a frightening conflagration possibly sparked by a broken 24-inch gas main, a massive fire in San Bruno on Thursday destroyed dozens of homes in the upscale hillside community, killed at least three people, injured an unknown number of others and sent scores of residents fleeing as firefighters battled the ferocious blaze.

Motorists from nearby Interstate 280 and eyewitnesses described the flames reaching as high as 60 feet into the air — shown on live television images — after the huge fireball ignited with a sudden explosion in the packed residential community, a few miles from the San Francisco International Airport.

Yasmine Kury, who lives in the apartment complex near the fire’s origin, saw black smoke drift over I-280, after a thunderous explosion rocked the Crestmoor community in the area of Skyline Boulevard and Sneath Lane about 6:15 p.m.

“We heard it and felt it and everyone ran out of the building,” Kury said. “It was a just a huge explosion.”

The noise was so deafening that residents at first thought a plane had crashed, but Pacific Gas & Electric officials initially said a two-foot-wide natural gas pipeline had erupted, fueling the flames that quickly began devouring homes and forced a widescale evacuation. PG&E later said it could not confirm that the cause was sparked by a pipeline explosion.

San Bruno city officials declared the community a local disaster area. At least 53 homes were heavily damaged or destroyed, and another 120 suffered some damage, according to San Bruno Fire Chief Dennis Haag. At least 100 residents have been evacuated. Between 150 to 200 firefighters were on scene at the six-alarm fire, with other agencies helping.

Lt. Gov. Abel Maldonado signed an emergency declaration late Thursday, according to spokesperson Erin Shaw.

Two brothers, Bob and Ed Pellegrini, live near the house at the center of the explosion, reported to have occurred at Claremont and Glenview. As the ground shook violently, they thought an earthquake had rattled the Bay Area. Then they saw the flames outside their window.

“It looked like hell on earth. I have never seen a ball of fire that huge,” Bob Pelligrini said.

It was too hot to escape out the front door, so the brothers ran out the back and up the hill, the fire chasing them. It felt like a blowtorch on the back of their necks, they said. Then they saw their house and four cars were destroyed in the fire.

“The house is gone,” Ed said. “I have nothing. Everything is gone. We’re homeless.”

As helicopters dropped water and fire retardant on the leaping flames, San Mateo County opened emergency centers and a shelter at the San Bruno Recreation Center while activating a reverse 911 message system to alert residents. The exact number of homes burned and injuries could not be confirmed late Thursday, though at least four people, including two critically injured, were taken to San Francisco and Daly City hospitals. And, the San Mateo County Coroner’s office confirmed one fatality.

The California Public Utilities Commission, meanwhile, is investigating the cause of the explosion and fire, working with local officials and federal agencies as well as PG&E. Some residents in the neighborhood reported “a really strong smell of gas” last week with PG&E responding at the time.

At Bayhill Shopping Center, residents huddled together in shock and tears as they watched the terrifying scene unfold on television.

Patty Blick, who lives on the Claremont Drive, was driving home work when she was suddenly met with flames and heat. “My house is gone. I’m just not really here right now,” she said, sniffling. “I just don’t want to leave even though I know nothing is there. I keep thinking I will find something.”

John McGlothlin, who lives on the same street, was at home when the explosion happened.

“To me, it felt like an earthquake. Hearing rumbling, movement, stuff like that,” said McGlothlin, who was buying a sweatshirt and other essentials at the shopping center where police initially directed many of the displaced residents.

In the San Bruno neighborhood where the explosion rattled the largely residential community, emergency vehicles blanketed the area.

Marilyn Siacotos, a neighbor near who lives at the intersection of Fairmont Drive and Concord Way, drove by and picked up a family of four, who lost their cat in the fire.

Siacotos, 76, escaped through the back door because the flames were licking down the front of her street.

“I didn’t look back,” she said. “I just got out before anybody (emergency responders) came.”

Siacotos, and the family members, who did not want their name used, said the explosion originated at a home in the immediate vicinity of Fairmont Drive, a one-block road enclosed on both sides by Claremont Drive.

None of them had any time to grab any belongings before fleeing the scene.

Many described a chaotic scene, with residents scrambling for their lives, some suffering burns and cuts as they escaped the intense, radiating heat. Others said the massive blaze was the first time such a tragedy of this magnitude has ever unfolded in San Bruno.

Retired San Bruno Fire Battalion chief Bob Hensel, who also had to evacuate, said it was biggest fire he had seen in decades. When he left the house, with his two cats behind, he saw his wife’s car bumpers melt from the heat.

“I heard a big whooshing sound and there was a boom. Stuff started hitting the house and then it got yellow outside and then real warm,” Hensel said.

Though Thursday’s explosion resulted from a possible ruptured natural gas main, it brought painful reminders of another similar tragedy in the Bay Area. In November 2004, a fuel pipeline killed five construction workers in Walnut Creek — the deadliest gasoline pipeline explosion since one that killed six people in Texas in 1983.

Late Thursday, firefighters, including crews from throughout the Bay Area, still struggled to control the blaze bounded by Crestmoor Canyon, Sneath Lane and Skyline Boulevard. PG&E crews, meanwhile, continued to work with emergency crews.

“What makes this fire so devastating and so difficult is essentially it creates the equivalent of an eight-alarm fire in the heart of a residential neighborhood,” Retired Contra Costa Fire Battalion Chief Dave George said. “It behaves differently than most other fires because it grows in all directions at the same time. Whatever it wants to do, it does.”

George said the heat of the fire would be upwards of 1,200 degrees, which could create radiant heat hot enough to burn a couch inside a brick home through the window.

“This is really a worst case scenario,” he said. “The closest thing to something like this is when a wildland fire hits a residential neighborhood.”

Bay Area News Group staff writers Sean Maher, Matthias Gafni and Roman Gokhman contributed to this report.

Contact Sandra Gonzales at 408-920-5778.