At a Christmas Eve gathering in 2008, a natural gas explosion in a suburban Sacramento neighborhood killed a 72-year-old man and injured his daughter and granddaughter. Investigators determined that Pacific Gas and Electric was to blame for a leak, but federal and state regulators never cited the utility for safety violations.

It was one example of what many experts and studies say is weak oversight of gas pipelines in the United States, a problem that has contributed to hundreds of pipeline episodes that have killed 60 people and injured 230 others in the last five years. Those figures do not include the final toll of the explosion of another Pacific Gas and Electric pipeline this month in San Bruno, Calif., that left seven people dead and more than 50 injured.

Though the cause of that explosion was still under investigation, it was the latest event to raise concerns among safety experts. Several independent government reviews, going back several years, have found systemic problems with the way the Pipeline and Hazardous Materials Safety Administration, the federal agency in charge of pipeline oversight, enforces safety rules.

In 2004, for example, the General Accounting Office documented how pipeline safety enforcement “needs further strengthening.” It noted that average fines of less than $30,000 offered little deterrence and that the agency had trouble collecting the fines.