SAN FRANCISCO (AP) — State regulators said Friday Pacific Gas & Electric Co. put the public at risk over the last three decades by allowing some of its pipelines to run at dangerously high pressures in cities throughout Northern and Central California.

A staff report issued by the California Public Utilities Commission said the company wrongly classified hundreds of miles of natural gas transmission lines, the same type that blew up in the deadly explosion in San Bruno.

That means PG&E broke state pipeline safety rules thousands of times in recent decades, because federal law requires utilities to perform more stringent inspections on lines in densely populated areas to ensure they are properly pressurized, the analysis said.

The findings by the California Public Utilities Commission staff were part of an investigation into whether the classification problems violated state and federal laws and contributed to the pipeline rupture.

PG&E already faces millions in fines in the wake of the Sept. 9, 2010, blast, which sparked a gas-fueled inferno that killed eight people and destroyed three dozen homes in the suburban enclave.

But the 3,062 violations identified in the report, which staff said resulted in about 16 million daily violations over time, could result in much higher penalties. The commission did not immediately provide a potential range for the fines.

"The most egregious violations are the segments that operated at pressures that were non-commensurate with pipeline specifications and, consequently, subjected pipelines to higher stresses and lower safety margins," the report said.

PG&E spokesman Dave Eisenhauer said the company was reviewing the report and would file an official response by July. After that, the proceeding will go before an administrative law judge and ultimately the full commission before it is approved.

"We admitted to the CPUC that there were gaps we had identified," he said. "The job of accurately classifying our gas pipelines is not to be taken lightly. We've completely changed our approach to training for this key role."

Months after the deadly explosion, however, California regulators said PG&E officials were still downplaying the dangers posed by their misclassified pipelines in a report from June last year.