Pacific Gas and Electric has disclosed that it had been running some of its natural gas pipelines at higher levels than what federal safety authorities recommend.
A ruptured pipeline last September triggered an explosion and fire that killed eight people.
CPUC Executive Director Paul Clanon called the revelation a serious failure with serious safety repercussions on Friday. The federal Pipeline and Hazardous Materials Safety Administration requires utilities to perform more stringent inspections on lines that run through highly populated areas.
"We hope we're nearing the end of the revelations about PG&E's poor safety efforts," Clanon said in a statement. "PG&E faces another investigation and more potential fines."
PG&E says it has lowered pressure on some lines.
The Associated Press contributed to this story.