People can call (800) 789-0550 or send an e-mail to SBFire@cpuc.ca.gov if they smelled the gas.
At about 6:15 p.m. Thursday, a 30-inch steel gas transmission pipeline ruptured in the Crestmoor Canyon neighborhood of San Bruno, causing a massive explosion and fire that killed four people and hospitalized 52 others.
Thirty-seven homes were destroyed and eight sustained major or minor damage.
One of the four people who died was Jacqueline Greig, a CPUC employee who is listed on the commission's telephone directory as part of its Division of Ratepayer Advocates.
Greig and her 13-year-old daughter Janessa were killed in the fire.
The CPUC is assisting in the investigation along with local, state, and federal agencies, including the National Transportation Safety Board, the lead investigator.
The CPUC has the responsibility of enforcement action if safety violations are found during the investigation.
PG&E President Chris Johns said Friday that the utility had no immediate knowledge of complaints of a prior gas leak, but that officials are aggressively investigating the claim.
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:
VIDEO: Firefighters saved homes despite challenges
VIDEO: Friday evening update on San Bruno explosion
VIDEO: Friday noon press conference
VIDEO: Friday morning press conference
RAW SKY7 VIDEO: Friday morning over San Bruno
VIDEO: ABC7 News morning update on explosion
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
Bay City News contributed to this report.