The truth is going to arrive slowly, and perhaps incompletely, in the investigation into the causes of the multiple Northern California wildfires that sprung into deadly strength the night of October 8. But according to an audit conducted over two years ago by the California Public Utilities Commission into PG&E's Sonoma division, one often cited potential culprit, power lines equipment, was found to be woefully behind in terms of scheduled maintenance.

As NBC Bay Area reports of the audit, which covered a five-year period from August 2010 to September 2015, PG&E was found to have completed 3,527 work orders past their scheduled due date.*

Further, the audit found that more than 50 pieces of overhead equipment had not received the annual inspections they require under state law. Britt Strottman, an attorney for the counties affected by the San Bruno pipeline fire and the Butte fire in 2015, tells NBC Bay Area, "PG&E has a history of neglecting its infrastructure and this is more evidence of that."

PG&E pushed back against the findings in the audit, which were released Monday, issuing a statement to the Chronicle saying that most of the work "cited as late had been completed by the end of 2011, several years before the audit took place."

But other audits by the CPUC, including a spot check of PG&E equipment in Cazadero, Guerneville, Rohnert Park, Santa Rosa, Sonoma and Windsor, suggest ongoing lack of maintenance in the very area that experts have surmised could have played a significant role in the ignition of the fires: vegetation too close to power lines. Per the Chron, "Problems found [in the spot-check] 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."

As the New York Times reports, fire investigators are closing in on where they think the ignition points were in Napa and Sonoma counties, where the deadliest and most destructive of the fires occurred.

"If there are high velocity winds, there’s every reason to suspect that power lines are a source,” says USGS fire expert Jon E. Keeley to the times. "We have many documented cases of power lines igniting fires during these high wind events."

All related coverage of the North Bay wildfires on SFist.

* This story has been updated to show that NBC Bay Area broke the news of the audit.