California regulators said today they will order Pacific Gas and Electric to survey all its natural gas lines in the state, after a massive gas line explosion in suburban San Francisco devastated a neighborhood and left at least four people dead.
As part of the order from the state's Public Utilities Commission, 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 its investigation.
News of the order came late today, after many residents of the San Bruno neighborhood were allowed to return to their homes for the first time since the blast Thursday.
Bruno 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.
Others whose were marked with yellow tags were only allowed to gather some clothes and belongings and leave.
The pipeline was known to be potentially dangerous. In a 2007 document, PG&E, which owns the line, said the pipeline, "ranks in the top 100 highest risk line sections," adding that the "risk of failure at this location is unacceptably high."
The document was part of a budget request to replace the line.
"This raises the question of what PG&E knew and when they knew it and whether better safety procedures could have avoided this horrible tragedy," said Mindy Spatt, of The Utilities Reform Network.
San Bruno's mayor said he was was unaware of the risk assessment.
"The whole thing is troubling to me," Mayor Jim Ruane said.
Investigators from the National Transportation Safety Board took measurements and pictures of pieces of the pipe that exploded, which is the focus of their investigation.
They plan to ship the damaged section of pipe to a lab in Washington for metallurgy tests to help determine whether sewer line work in the neighborhood could have been a factor in the explosion.
"That's one of the things the metallurgy examination will help ascertain, because we'll be able to determine was the failure in the pipeline due to fatigue or was it because of an impact in the case of construction," Christopher Hart of the NTSB said.
Police have officially said that five people are missing.
Authorities are attempting to confirm whether the remains they've discovered are human and then identify the victims, said San Bruno County Coroner Robert Foucrault.
State and local politicians vowed Saturday to get to the bottom of what caused the massive explosion and fire.
The explosion left more than 60 people injured and destroyed 37 of homes in the community, which is in the hills just south of San Francisco.