San Bruno, CA – Fire crews tried to douse the remnants of an enormous blaze and account for the residents of dozens of homes Friday after a gas line ruptured and an explosion ripped through in a neighborhood near San Francisco, killing at least four people and likely more.

Emergency workers haven’t been able to get into all the homes and said there could be more casualties. Earlier Friday, officials said at least six people were killed before revising the official number to four. At least 50 people were hurt, with three suffering critical burns in the explosion Thursday evening that left a giant crater and sent flames tearing through the middle-class neighborhood of 1960s-era homes in hills overlooking San Francisco, the bay and the airport.

“Now that there is daylight, there is going to be even more heartache and more difficult times ahead. Individuals are going back and seeing the devastation of this fire,” said San Francisco state Sen. Leland Yee, who was at the scene.

Pacific Gas and Electric Co. President Chris Johns said Friday morning a 30-inch gas pipe ruptured about three feet underground just before 6:30 p.m Thursday, but crews still haven’t been able to determine the cause of the rupture or the blast because they can’t get close enough. The blaze was 75 percent contained by midmorning, fire officials said.

Johns said the company has heard reports that some residents smelled gas in the area before the blast.

“Right now, we haven’t got confirmation about that, but we have records that we are going back right this minute to try to confirm what exactly those phone calls look like and when they occurred, and we will report back as soon as we know something.”

After the initial blast, flames reached as high as 100 feet as the fire fueled itself on burning homes, leaving some in total ruins and reducing parked automobiles to burned out hulks.

It’s not the first time a deadly explosion on a PG&E gas line has devastated a Northern California neighborhood.

On Christmas Eve 2008 an explosion killed a 72-year-old man in the Sacramento suburb of Rancho Cordova, destroyed one home and seriously damaged others.

The National Transportation Safety Board’s final report said PG&E used a wrong pipe to repair the gas line two years before the explosion. Rancho Cordova residents had reported of a gas smell in the area before the blast.

In response to the NTSB’s findings, the company said it had taken “extraordinary measures” to ensure a blast like that would never happen again.

The NTSB has sent a four-member team to San Bruno to investigate Thursday’s blast.

Four firefighters suffered minor smoke inhalation injuries and were treated and released within a couple hours of the blast, said Fire Chief Dennis Haag.

Haag said crews walked through the neighborhood Friday morning and revised the damage estimate to 38 structures destroyed and seven significantly damaged. Dozens of other homes suffered less severe damage in the fire, which burned 15 acres.

Gov. Abel Maldonado, acting governor while Gov. Arnold Schwarzenegger was in Asia on a trade mission, declared a state of emergency in San Mateo County.

Rep. Jackie Speier, a Democrat who represents San Mateo County, said she was working to secure federal disaster assistance for residents and businesses affected by the fire.

“This is an extraordinary community, it’s extremely tight-knit. Generations of families have lived here forever. And we will all come together. We will restore the homes and lives of all these people.”

Stephanie Mullen, Associated Press news editor for photos based in San Francisco, was attending children’s soccer practice with her two children and husband at Crestmoor High School when she saw the blast at 6:14 p.m.

“First, it was a low deep roar and everybody looked up, and we all knew something big was happening,” she said. “Then there was a huge explosion with a ball of fire that went up behind the high school several thousand feet into the sky.

“Everybody grabbed their children and ran and put their children in their cars,” Mullen said. “It was very clear something awful had happened.”

Several minutes later, Mullen was near the fire scene, about a half-mile away. She said she could feel the heat of the fire on her face although she was three or four blocks away from the blaze. It appeared the fireball was big enough to have engulfed at least several homes.

“I could see families in the backyards of the homes next to where the fire was, bundling their children and trying to get them out of the backyards,” she recounted.

She said people in the neighborhood were yelling, “This is awful” and “My family is down there.”