A 2015 audit by California utility regulators faulted Pacific Gas and Electric Co. for thousands of late maintenance jobs and repairs to its electricity distribution network in Sonoma County, where state investigators are now examining whether the company’s power lines played a role in this month’s deadly fires.

The document, released Monday by the California Public Utilities Commission, appears to be the last time the regulatory agency audited PG&E’s maintenance of distribution lines, poles and other equipment within the county.

It found that over a five-year period, from August 2010 to September 2015, PG&E had finished 3,527 work orders past their scheduled due date. The audit does not provide much detail on the types of work involved other than saying it involved both overhead and underground facilities.

The audit also said PG&E had inspected some of its overhead and underground equipment in the county a year late.

A PG&E spokesman said Monday that the majority of the work cited as late had been completed by the end of 2011, several years before the audit took place.

PG&E’s maintenance of its power lines and poles has come under close scrutiny since a series of wildfires erupted in the North Bay on Oct. 8 in the midst of a fierce wind storm. Investigators with the California Department of Forestry and Fire Protection, or Cal Fire, are looking at the possibility that power lines tangling with tree branches in the wind could have sparked the fires. A Chronicle reporter who visited the suspected origin points of several of the fires found downed power lines.

The audit, one of several posted online by the utilities commission, included spot-check inspections of PG&E equipment in Cazadero, Guerneville, Rohnert Park, Santa Rosa, Sonoma and Windsor. Problems found include one instance of vegetation growing too close to a power line, one of vegetation obstructing the climbing space on a pole and several instances of improperly installed guy wires, which help hold a pole in place.

David R. Baker is a San Francisco Chronicle staff writer. Email: dbaker@sfchronicle.com Twitter: @DavidBakerSF