The order issued by the state's Public Utilities Commission Sunday comes after the explosion in a San Bruno neighborhood Thursday destroyed dozens of homes and left at least 60 injured, some critically.
As part of the order, the commission says PG&E must run leak surveys on all natural gas lines, with priority given to higher pressure pipelines and to lines in areas of high population density.
The commission also plans to appoint an independent expert panel to help with their investigation.
Some residents return to their homes
Many San Bruno residents returned to their homes Sunday for the first time since Thursday's tragic fire and some may be smelling the odor of natural gas as PG&E crews work to restore service.
Officials held a briefing Sunday morning explaining the latest on the situation in the charred neighborhood. The San Mateo County coroner has revised the death toll back to four, down from seven reported Saturday night. Six people remain missing and cadaver dogs will resume their search today in the burned out area.
On Sunday, San Bruno residents affected by the fire got the best news they have received in the past few days. City Manager Connie Jackson said during a morning news briefing that many residents in the area would be able to return home Sunday and stay in their homes. However, may others would not be as lucky.
Some residents did return home after being homeless for three days, escorted by PG&E crews who turned on their power and gas.
Thursday's fire destroyed 37 homes. Residents' homes that were yellow-tagged were only be allowed to recover clothes and belongings and had to return to their hotel rooms.
The NTSB is continuing to investigate the 30-inch pipeline which caused the explosion and fire. The blast lifted a 28-foot section of the pipe out of the ground creating a crater 167 feet long and 26 feet wide. While the investigation continues, San Bruno officials only allowed resident re-entry in stages. The residents gathered at Skyline College at noon and had to bring a photo ID.
Investigators were cautious in letting residents back in the neighborhood since they spent another day searching through the ashes for any human remains.
"We have four bodies. Three of them have been positively identified. We're working on the fourth and as far as the remains that have been located, we're in the process of doing forensic tests," Robert J. Foucrault said.
Meeting for residents unable to go home
On Monday morning at 10 a.m., there will be a briefing for residents whose homes were destroyed or red-tagged. Those areas are still off-limits due to their hazardous condition and the ongoing investigation. That meeting will be at the San Bruno Senior Center at 155 Crystal Springs Road.
Tempers flare at town hall meeting
Things got pretty heated and emotional during a town hall meeting in San Bruno Saturday. Residents packed Saint Roberts Catholic Church to learn about what is being done to help them.
One person pressed PG&E for answers, asking if the locations of other pipelines can be released to the public. At one point, Geisha Williams with PG&E was interrupted by a member of the audience who was then addressed by another official.
"This meeting will be conducted in a proper manner and if you can't hold yourself that way, we will escort you out, alright? This city's been through enough grief," a man said prompting applause.
Many displaced residents simply avoided the meeting and focused on other tasks at the service center like dealing with their insurance companies.
Gas pipeline was classified "high risk"
State authorities say the section of the gas pipe that exploded was classified as "high-risk" because of its close proximity to homes. Nationwide, only about 7 percent of gas lines have that classification.
Right away, federal investigators noticed something curious about the 28-foot section of pipe that blew out of the ground. It was not solid and seamless. Rather, it was made up of smaller segments welded together. The NTSB wants to know why.
"It's not necessarily a repair. There are lots of reasons to have segmented pipe like this and that's one of the things we're exploring is why was this piece of pipe segmented. Because, it's obviously more expensive to have segmented pipe than to have un-segmented," said NTSB Vice Chairman Christopher Hart.
The NTSB confirms that PG&E had manual valves on either side of the break and not automatic valves to stop the flow of gas.
The pipeline that exploded was first installed back in 1948, when there were fewer homes in the area, and was scheduled to be swapped for new 24-inch pipe. Because the area is so heavily populated now, the Public Utilities Commission designated the pipeline "high risk."
"That certainly increases, in our estimation, the need to look at that issue of whether there should be automatic shut-off valves whenever there's some kind of a massive leak in the pipe which would be signaled by a pressure drop. So, that's one of the issues we'll be looking at," Hart said.
The latest measurement shows the crater left by the blast to be 167 feet long and 26 feet wide. The soil is too unstable to determine how deep it is. PG&E now says it started inspecting three major gas transmission lines in the peninsula. Sen. Barbara Boxer, D-Calif., is calling on state and federal regulators to accelerate their inspections of pipelines statewide.
"There could be corrosion. There could be faulty parts in these pipelines. There could also be excavation. So, we have to be very clear that we're trying to prevent this from every happening again and the first way, it seems to me, is to do these inspections in a priority order where you have population," she said Saturday.
By itself, natural gas has no odor. The NTSB confirmed that the gas in the line was in fact odorized, creating that familiar natural gas smell that some residents claim they noticed in the days leading up to the catastrophe.
One resident says he saw a PG&E worker on Glenview Drive two days before the explosion. He described the worker as having a hand-held device that is used to check for indications of gas.
On Saturday, PG&E President Chris Johns addressed the reports and said officials have not found any records of calls to PG&E about a problem in the first nine days of September, or a record of their crews being in the area.
San Bruno police have declared the area crime scene. The National Transportation Safety Board said Friday that it has sent a four-member team to San Bruno to investigate.
CPUC sets up number to reported gas smell
The California Public Utilities Commission has established a toll-free number and e-mail address for anyone who noticed the smell. People can call (800) 789-0550 or send an e-mail SBFire@cpuc.ca.gov if they smelled the gas.
The NTSB has also set up a tip line for their investigation. They are interested in reports of a natural gas order or any plants dying. You can e-mail information or armature video related to this case to: firstname.lastname@example.org
Coroner identifies victims
Late Friday night, the San Mateo County Coroner's Office released the names of three of the people who were killed. Two of the victims are mother and daughter -- 44-year-old Jacqueline Greig and 13-year-old Janessa Grieg. Greig worked with the California Public Utilities Commission. The other victim has been identified as 20-year-old Jessica Morales. As of late Saturday evening, seven people were dead and another six were missing.
The names of the other victims have not yet been released, however Faye Wharton told ABC7 the body of her 80-year-old grandmother was found in the ruins of her home, which is right next to the explosion. She received word from authorities late Friday night. Her two aunts and uncle were also in the house. They made it out alive, but were severely burned.
Gas pipeline explodes
At 6:24 p.m. Thursday, an explosion and fireball erupted from near the intersection near Glenview Drive and Earl Avenue. People as far as one-half mile away say they felt the boom and heat of the explosion.
A NTSB official said Saturday that a 28-foot long section of the pipe was blown 100 feet away from its original location. The explosion left a crater 167-feet long and 26-feet wide.
After burning out of control for hours, the blaze was finally contained Friday afternoon, and 52 people were transported to area hospitals -- three with critical burns. Four firefighters sustained minor injuries.
There was one report of a person looting one of the burned houses. That person also charged for assaulting an officer and arrested for trying to flee.
Rescue crews and home inspection crews performed a house-to-house search through the neighborhood. There were 37 structures destroyed and eight more homes that suffered major or minor damage. See which homes were destroyed here.
Firefighting efforts hindered
Several factors conspired to hinder firefighting efforts. The natural gas explosion ruptured a water main, shutting off water to many of the fire hydrants in the fire zone. It took about half an hour to reroute the water main.
In the meantime, firefighters went searching for the nearest working hydrant, a few thousand feet away. San Bruno's fire chief said given the extent of the blazes, he is not sure a swifter response would have made much of a difference.
Injures at the Bothin Burn Center
Four burn victims are being treated at the Bothin Burn Center at St. Francis Hospital in San Francisco. That center is internationally recognized for being one of the most advanced acute care centers for burn victims.
All of the victims are in critical condition according to Dr. Michael Kulick, who was the surgeon on duty when they were brought in Thursday night. Three patients have burns over 50 percent of their bodies, and the other one has burns on 40 percent of the body. Two doctors and 40 nurses were there to accept the patients.
What the victims face is difficult, with many procedures. They are breathing with a tube, they have been given fluids, and are stable. On Sunday Kulick will remove when he calls non-viable tissue. The final phase will be grafting skin from areas not burned onto the burned area. But all of these procedures could take up to two years.
The public has responded to the plight of San Bruno residents. At the Blood Centers of the Pacific, the wait is up to two hours to give blood. So many people turned out that they are suggesting donors come back another time, since they will need blood in the coming weeks.
Leaders offer aid
Lieutenant Gov. Abel Maldonado has declared a state of emergency in the area and joined other leaders in San Bruno Friday. Maldonado is acting governor while Gov. Arnold Schwarzenegger is out of the country. Maldonado has briefed Schwarzenegger on the situation. Maria Shriver also visited the area on Friday.
PG&E President Chris Johns said at a Friday press conference that the company is committed to providing temporary housing, food, clothing and other essential needs to the displaced residents.
The state is also taking steps to ease the struggles of the victims. Maldonado announced that the state would waive fees for people replacing their drivers licenses and birth certificates as well as waive the waiting period for people looking for unemployment assistance.
Are big pipelines safe?
Many people are wondering what the dangers are living close to large natural gas pipelines. ABC7's Dan Noyes looks into the safety issues of these major pipelines. More on that story here
ABC7 Breaking News Coverage:
Some San Bruno residents allowed to return
RAW: NTSB Sunday afternoon update
RAW SKY7 VIDEO: Friday morning over San Bruno
VIDEO: Photographer's first-hand account of devastation
VIDEO: Eyewitness account
PHOTOS: San Bruno explosion
VIDEO: "I thought - this is judgment day"
VIDEO: Fire consumes neighborhood
VIDEO: Photographer captures images moments after blast
The Associated Press and Bay City News contributed to this report.