Gerry Shih/The Bay Citizen

Paramedics evacuate seniors at the corner of Sneath Lane and Claremont Drive Sept. 9

Updated Friday, Sept. 10 at 11:12 p.m.

As rescue workers and a dozen police dogs combed the smoldering Crestmoor neighborhood in San Bruno for bodies Friday, federal agents opened an investigation into the cause of Thursday's natural gas explosion. The death toll climbed to four, with more than 50 people injured and an unknown number still missing.

The morning-after picture of the disaster was one of charred devastation, with an entire residential enclave reduced to ash. Officials said that 37 homes were destroyed, down from an original estimate of 53, and eight more were severely damaged. A growing army of government agencies and volunteers was descending on a San Bruno community center to assist with the aftermath.

By 2 p.m. Friday, the fire was reported to be fully contained with a few hot spots, according to the city's fire chief. By 6 p.m., search teams had covered 95 percent of the area looking for victims, with the rest of the area still too hot to enter. Six canine units were slated to resume the search on Saturday.

PG&E said gas to the area had been turned off, but company officials refused to disclose how long it took to shut down the flow of gas that stoked the raging fire well into the evening after the blast occurred shortly after 6 p.m.

Investigators from the National Transportation Safety Board joined others from the California Public Utilities Commission to try to sort out what happened, as a growing number of residents complained that PG&E knew of a leak and may even have performed work in the area in the days leading up to the disaster.

A local state of emergency was declared after the huge explosion. Emergency vehicles from around the Bay Area streamed to the scene; dozens were still on site Friday. PG&E confirmed Thursday that one of its natural gas transmission lines ruptured, causing the fire, but officials continued to say Friday that they did not know why the rupture occurred. Residents who witnessed the explosion described a roaring sound like that of a jet engine, followed by a thud so enormous it felt "like an earthquake."

Don Ford, a photo journalist with CBS 5, visited the epicenter of the blast after much of the fire had subsided late Thursday night and said the explosion left a crater 15 feet deep and with a radius of 40 to 50 feet. Ford said the fire literally liquefied the street, leaving nothing but dirt, and left homes, trees, sidewalks and everything else that had been standing in ashes.

"The heat wave just radiated out and destroyed everything in its path for hundreds and hundreds of yards," Ford said on CBS 5. "Tomorrow morning when the sun comes up it's going to be something out of Dante."

For more than an hour, the flames shot up dozens of feet into the air, with a plume of smoke extending up thousands of feet, visible from as far away as Oakland and Marin County. Houses in the blocks nearby burst into flames and burned down to the foundation. The fire was so hot that witnesses could feel the heat through their car doors from several blocks away.

The extreme heat initially prevented firefighters from approaching the fire; they set up a triage center, but were reportedly forced to remain one-half to one-quarter mile away from the flames for at least an hour. Helicopters and air tankers dropped fire retardant around the perimeter of the fire to try to prevent it from spreading. As of 8 p.m., firefighters were spraying some burning homes with water.

Firefighting efforts were hampered by the apparent destruction of a water main, but by 8:00 p.m. Thursday, what had been a massive, pulsating fireball was reduced to a huge plume of orange glowing smoke. As of Friday morning the fire was 75 percent contained, but fire officials were still concerened about hot spots and possible spread into the wildlands above the neighborhood. Humid weather and low winds on Friday morning were aiding the effort.

Three firefighters were injured fighting the fire and taken to a hospital. San Bruno fire Chief Dennis Haag said at a press conference late Thursday night that PG&E had shut off the distribution line to the area, but there was still residual gas in the pipes feeding the fire.

The damage was centered in the neighborhood bordered by Sneath Lane, Skyline Boulevard and San Bruno Avenue. Cars were not allowed to enter the area near the fire Thursday night, and some vehicles were stuck in traffic nearby for more than an hour.

Besides the four fatalities, at least 42 victims of the fire were treated at local hospitals Thursday night, including Seton Medical Center in Daly City and Kaiser Permanente in South San Francisco. San Francisco General Hospital, the official trauma center for northern San Mateo County, is currently caring for four victims of the fire, all of whom are in critical condition. They include two burn victims — a man in his 50s and a woman in her 80s. Another woman in her 80s and a woman in her 60s suffered from smoke inhalation. Saint Francis Memorial Hospital is now treating four victims at its burn center, three of whom have critical injuries and one of whom has serious injuries. All four of those patients were stable early Friday afternoon.

The Blood Centers of the Pacific has reported an "overwhelming response" to a blood emergency it issued Thursday night. As a result, blood centers are experiencing long wait times. Those wishing to donate blood to help the victims of the fire are now being asked to hold off until next week or later. "It is essential that the blood currently being used be replenished in the coming weeks," the center said.

The San Mateo County Office of Emergency Services set up an emergency shelter for evacuees at the San Bruno Recreation Center at 251 City Park Way, where the Red Cross is providing help. The telephone number there is 650-616-7180. An additional evacuation center has been set up at the senior center at 1555 Crystal Springs Road. Anyone in need of shelter or assistance can reach the Red Cross at 888-443-5722. Residents searching for loved ones can write a message on a sign-in sheet posted at the Bayhill Shopping Center.

Speaking at a press conference Thursday night, San Bruno Mayor Jim Ruane said that a "terrible, terrible tragedy has fallen on our city."

"This is going to be a long haul for our city and our residents in the weeks to come," Ruane said.

Lt. Gov. Abel Maldonado, who is the acting governor as Gov. Arnold Schwarzenegger is out of the country, said a state of emergency has been declared for the area.

State Sen. Leland Yee, whose district includes San Bruno, said the declaration will enable the release of millions of dollars in assistance.

Speaking on CBS 5 Thursday night, Yee, a Democrat, vowed that state agencies would investigate the matter to determine the cause of the accident.

"We're absolutely committed to finding the exact cause and those individuals who contributed to this disaster, they will, in fact, be held accountable," Yee said.

On Friday, the Federal Emergency Management Agency announced it had authorized federal funds to help state and local authorities fight the fire. FEMA will reimburse 75 percent of firefighting costs, including for supplies, shelters and traffic control.

"I want to assure [San Bruno residents] and our local and state partners that FEMA is here to make sure that California has the resources needed to fight this fire, and that the federal government will remain with the state every step of the way," said regional administrator Nancy Ward in a statement.

Initially, some observers speculated that the fire might have been caused by a gas station blowing up, but it soon became clear that there was no gas station in the immediate area of the explosion. The Federal Aviation Administration and San Francisco International Airport confirmed no planes were missing.

"There's no indication an aircraft was involved. There's nothing to lead us to believe it was an aircraft," said the airport's duty manager on duty.

It's not clear whether the fire had an effect on aircraft routing from SFO.

All schools in the San Bruno Park School District were closed on Friday, but will reopen Monday, Sept. 13. Classes were canceled Friday at Highlands Christian Schools at 1900 Monterey Drive, but the school hosted a community prayer session.

Click here for complete coverage of the San Bruno explosion and fire.