California regulators voted Thursday to establish a high-level, independent panel to investigate the San Bruno gas line explosion that killed seven people and torched dozens of homes in the hills overlooking San Francisco Bay.

The resolution adopted 4-0 by the California Public Utilities Commission also called for a review of management practices at Pacific Gas & Electric Co., the utility that owns and operates the ruptured line.

Regulators vowed to probe what the utility and the commission could have done to prevent the disaster.

"We have to look at every facet of the factors that led up to this accident and, particularly, not be afraid to look in the mirror," commissioner Nancy Ryan said at the packed public meeting webcast from San Francisco.

The expert panel will work independently from the National Transportation Safety Board, the lead federal agency investigating the cause of the Sept. 9 blast that leveled nearly 40 homes.

Commissioners were pressing PG&E to cover the cost of the panel's work with shareholder funds, not money from ratepayers.

Federal investigators were still examining why gas began leaking from the 44-year-old transmission line and sent a fireball shooting hundreds of feet above the suburban San Francisco neighborhood.

NTSB officials trucked segments of the exploded pipe to its laboratories and were conducting tests to determine if corrosion, material failure or other problems contributed to the leak and explosion. They planned to issue a preliminary report in the coming weeks.

PG&E has not released information concerning what problems might have shown up in prior inspections of the 30-inch line but earlier this week publicized a list of the utility's 100 riskiest transmission pipeline segments, based on maintenance records and planned construction projects that could threaten to puncture specific lines.

The segment of pipe that blew up in San Bruno was not on the list.

The company said it will wait to learn the cause of the explosion before determining if its inspectors missed something.

Commissioners began the meeting with a moment of silence to remember the victims, including their colleague Jacqueline Greig, who would have celebrated her 45th birthday Thursday.

Greig and her 13-year-old daughter Janessa died in the massive blast that left a crater behind their home.

Greig was part of a small commission team that advocates for consumer and environmental protections pertaining to natural gas. She spent part of the summer evaluating PG&E's expansion plans and investment proposals to replace out-of-date pipes.

"We at the PUC have a very special way that we can serve Jacki and Janessa, and that's by doing our job," Executive Director Paul Clanon said.

Also Thursday, cleanup crews started to remove the foundations of the 37 homes destroyed in the explosion.

The goal is to leave homeowners with a clean slate, so they can build anew, San Mateo County environmental health division director Dean Peterson said.