New photographic evidence indicates tree contact with two PG&E power lines – not the private hilltop electrical system state investigators have blamed – caused the devastating Tubbs fire, according to an expert with four decades of experience investigating electrical fires.

Until now, the second most destructive fire in state history stands as the only one of a two-year string of Northern California wildfires Cal Fire has not blamed on PG&E equipment. Cal Fire says in its report this year that the fire that started on October 8, 2017, was sparked somewhere along an unpermitted, substandard electrical system on a hilltop property along Bennett Lane in Calistoga.

But photos of two PG&E lines – recently obtained by NBC Bay Area’s Investigative unit – show telltale marks of arcing far from that home, says veteran electrical engineer Ken Buske, who has examined the cause of 1,000 fires over four decades.

Arcing is the burst of energy, akin to lightning, often associated with high voltage lines slapping against each other in high winds or contact with vegetation.

The photos are of two adjacent PG&E wires that had fed the hilltop property, after PG&E replaced them earlier this year as part of what it says was system hardening efforts against wildfire.

The photos show boil-like marks on what had been two adjacent 12,000 volt copper lines. Those wires, PG&E says, are now being preserved.

“This is where the fire started,” Buske said, pointing to the photos and the location of the marks on the top of the wires as strong evidence of tree contact at a location that sources say is about 30 feet from Bennett Lane. That spot is some 100 yards from the area of origin identified in Cal Fire’s report.

Based on the marks, Buske offered a much different scenario than Cal Fire’s report.

“There’s a bright flash, an electric flow -- like lightning between the portion of the wire, the top wire and some vegetation, and there’s a similar event with the other wire,” Buske said.

He says a surveillance video that NBC Bay Area previously broadcast is additional evidence. The recording shows that at 9:20 p.m., well before the fire became visible, there was a bright flash of light to the right of the image, not far from where the arc marks were found. Buske says the intensity of the light is strong evidence of arcing.

The timing of the flash also corresponds to the exact moment fuses and a power outage that cut power to the private hilltop property Cal Fire blames for the fire.

Given the report doesn’t account for even the potential that arcing sparked the fire, Buske offered a blunt assessment of Cal Fire’s findings.

“The fire report is wrong,” he said.

Cal Fire has not responded to questions about potential new evidence of arcing, instead standing by its findings that clear PG&E.

PG&E’s CEO, Bill Johnson, says Cal Fire got it right.

“There were 21 fires,” Johnson said after a federal court status hearing earlier this month on PG&E wildfire prevention efforts. “Cal Fire said PG&E caused 20 of them, and didn’t cause the other one, and I think we should have a little confidence in their ability to determine things.”

But State Sen. Jerry Hill isn’t so sure, especially since Cal Fire has so far seemed unwilling to look at any evidence that casts doubt on its findings.

“It’s outrageous,” he said, “that they’ve kind of dug in their heels and said we’re not going to do that.”

Hill says state investigators should think twice when they point the finger and then refuse to reconsider.

“We’re going to really force this -- because when you don’t blame the right people, you don’t hold the right people responsible for this. That’s not justice…”

Buske says based on the evidence he has reviewed, Cal Fire needs to start the Tubbs fire probe from scratch.

“There’s a big problem,” he said. “The Tubbs fire isn’t somebody’s burnt chicken coop. A lot of people suffered a lot in the fire and they deserved a good fire report.”

Whatever Cal Fire does now, a San Francisco jury is set to decide in January what role, if any, PG&E played in the fire.