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A federal court in San Francisco tentatively found that equipment owned by Northern California utility Pacific Gas and Electric was "the single most recurring cause" in deadly wildfires that have plagued the state since 2017.

U.S. District Court Judge William Alsup made the finding Thursday in a case related to PG&E's response to the deadly 2010 San Bruno gas pipeline explosion.

"The Court tentatively finds that the single most recurring cause of the large 2017 and 2018 wildfires attributable to PG&E’s equipment has been the susceptibility of PG&E’s distribution lines to trees or limbs falling onto them during high-wind events," his order in the case reads.

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"The power conductors are almost always uninsulated," Alsup wrote. "When the conductors are pushed together by falling trees or limbs, electrical sparks drop into the vegetation below. During the wildfire season when the vegetation is dry, these electrical sparks pose an extreme danger of igniting a wildfire."

A home burns in Fountaingrove on Oct. 9, 2017 in Santa Rosa, Calif. More than a dozen wildfires whipped by powerful winds been burning though California wine country. The flames have destroyed at least 1,500 homes and businesses and sent thousands of people fleeing. Kent Porter / The Press Democrat via AP

In a statement, PG&E said it was still reviewing the judge's tentative conclusion.

"PG&E’s most important responsibility is the safety of our customers and the communities we serve," the utility said. "We are aware of Judge Alsup’s latest order and are currently reviewing. We are committed to complying with all rules and regulations that apply to our work, while working together with our state and community partners and across all sectors and disciplines to develop comprehensive, long-term safety solutions for the future."

Earlier this month, it was reported that the utility was exploring possibly filing for bankruptcy because of liabilities related to fires authorities say were caused by PG&E.

Scott McLean, deputy chief of communication for the California Department of Forestry and Fire Protection, said his agency has determined that the utility is at fault for 12 of 17 fires in 2017; it has not yet made conclusions about 2018's fires, including the deadly Camp Fire in Butte County.

Alsup has ordered the utility to determine if it had any culpability in the blaze, which killed at least 88 and wiped out the town of Paradise. In a document obtained by CNBC, PG&E acknowledged that its equipment may have sparked the blaze.

The judge wants to determine whether the utility violated the terms of its agreement with the government on the San Bruno explosion.