California firefighters were battling a huge fire still raging on Friday hours after a gas pipeline exploded destroying or damaging more than 170 homes, amid reports at least six people had been killed.
The massive explosion and inferno ripped through a neighborhood in San Bruno near San Francisco, leaving residents shocked by the sudden devastation.
San Bruno fire chief Charlie Barringer told the Los Angeles Times at least six people were dead, and the toll was expected to rise. CNN television reported three people had been killed.
"I thought a 747 had landed on us," Barringer said. "It shook our station right to its foundation."
The explosion even destroyed the grid of water mains and they were left without water. "We were overwhelmed. We had multiple neighborhoods on fire," he said.
California's acting governor Abel Maldonado, filling in for Governor Arnold Schwarzenegger who is visiting Asia, declared a state of emergency for the city just two miles (three kilometers) west of the San Francisco International Airport.
"It looks like a bomb went off," Maldonado said after touring the destruction. "I'm sure we'll find people who have not made it," he told CNN.
The devastation - which included the loss of 53 homes, damage to at least 120 more, and injuries to up to 38 people - was startling, said Maldonado.
About 100 residents fled for their lives, many weeping while others paused to capture the chaotic scene on cell phone cameras.
"I heard a sound like a low flying plane, then all of a sudden the house shook," said Tina DiIoia, who was with her baby in their condominium, when the explosion occurred about a kilometer away.
"Then there was another explosion. I went outside and there was debris falling from the air."
"It looks like the entire mountainside is burning," DiIoia said.
"It was just a huge explosion," another one resident recounted. "More than that, we felt the heat. It was a huge heat wave that sucked the air out for a minute."
Acting governor Maldonado said he saw several cars still in the driveways of homes that were destroyed or damaged in the disaster.
"That tells me people didn't leave, and that is of grave concern," he said. "The numbers are going to change all morning. It's going to be sad."
San Bruno Mayor Jim Ruane confirmed that it was a high-pressure, 24-inch-wide (60-centimeter-wide) natural gas line that ruptured, causing the thunderous explosion that triggered the inferno.
"A terrible, terrible tragedy has fallen on our city," Ruane said. The top priority, he said, was "making sure our citizens are safe."
"This is going to be a long haul for the city and our residents," he added.
In one street a dozen homes were seen engulfed in flames. Witnesses spoke of a smouldering crater the size of a city intersection, while scores of raging fires turned San Bruno's smoke-filled night sky orange.
Up to 200 firefighters were dispatched to battle the blaze, but they were no match for flames whose intense heat reportedly melted fire truck windows and car taillights several dozen yards (meters) from the flames.
Pacific Gas & Electric spokesman Jeff Smith described the fire as "an absolutely horrible situation," and said that if it turns out the utility was to blame, "we will absolutely take accountability for it."
Helicopters and airplanes were seen dumping water and fire retardant chemicals in an effort to stanch the flames.
A huge fountain of flames blasted from the ground like a blowtorch where the pipe was ruptured and fire spread relentlessly to houses in several directions.
More than 30 people were treated at local hospitals, with emergency rooms going on alert and some victims rushed to burn units, according to emergency workers.
"This is really a tragedy," said Kaiser Permanente medical facility spokesman Karl Sonkin. "We are caring for people as best we can."