With three-quarters of the homes searched by rescue dogs, and the rest too hot to enter, investigators probed the scene for clues on the cause of the blast on Thursday evening.
Firefighters on Friday had largely contained a fire caused by a thunderous gas pipeline explosion that killed at least four people and destroyed 38 homes in a San Francisco suburb.
With three-quarters of the homes searched by rescue dogs, and the rest too hot to enter, investigators probed the scene for clues on the cause of the blast on Thursday evening in San Bruno, a small city near San Francisco International Airport.
The ruptured pipeline belongs to utility Pacific Gas & Electric Co, and shares of parent company PG&E Corp dropped more than 8% on Friday.
California Lieutenant governor Abel Maldonado, standing in for Governor Arnold Schwarzenegger who was on a trade mission in Asia, said he wanted to know more about reports of people calling PG&E about smelling gas prior to the explosion.
"The investigation is going on," Maldonado told Reuters. "There is going to be some accountability. The pipeline is owned by PG&E."
Four people were killed and 52 were injured, officials said. A few
hundred firefighters remained at the site.
"We have requested now two additional urban search and rescue teams to assist us as there's quite a bit of rubble and debris that has to be cleared," San Bruno fire chief Dennis Haag told a news conference on Friday afternoon.
Maldonado, who declared a state of emergency to hurry assistance to the city and victims, saw melted cars and sewage on the street when he toured the area.
The blast left a large crater, and residents said it was so strong they first thought it was an earthquake or plane crash.
"The flames were so surreal. It was like out of a sci-fi movie," said Kaila Uniacke, 17, who was at home with her brother when they heard the blast at about 6pm local time on Thursday.
Drivers on their way home from work said they could see the flames from the freeway. Some streets in the area were jammed with cars after the explosion as residents fled in a panic.
Connie Morales said the blast sounded like "horrible, horrible thunder."
"Then it roared," she added. "It kept going and going and going."
Officials had not determined what happened, according to PG&E President Chris Johns, who could not immediately comment on the reports of residents smelling gas before the blast.
"But we have records that we are going back right this minute to try to confirm what exactly those phone calls looked like and when they occurred," Johns told a news conference.
PG&E isolated the damaged section of the 30-inch (76-cm) steel gas transmission pipeline. The National Transportation Safety Board, which investigates gas leaks, and the California Public Utilities Commission have started investigations.
PG&E shares fell to $44.21, their lowest level since July.
PG&E bonds also lost value as investors worried about potential liability. But Phil Adams, at corporate bond research firm Gimme Credit, said past experience showed insurance would likely cover the cost.
"This will play out over the next several years, and it is our guess that the ultimate financial impact to PG&E will be minimal," Adams wrote in a research note.
The utility said in a statement on Friday it had about $992 million in liability insurance for fire damage.
But Standard & Poors Ratings Services later said it may cut its ratings on PG&E debt, citing factors including liability as well as reputational damage and the potential need for the utility to upgrade its infrastructure.
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