SAN FRANCISCO (AP) — Federal investigators have taken possession of a Pacific Gas and Electric Co. utility transmission pole and attached equipment in a criminal probe into what started a Northern California fire that has become the largest in the state this year, the utility said in a regulatory filing Monday.

U.S. Forest Service officials indicated to PG&E that an initial assessment showed the Mosquito Fire started near one of its power lines on National Forest lands, the Oakland-based utility said in its filing with the Securities and Exchange Commission.

Federal investigators removed the pole and equipment on Saturday, the utility said.

The Mosquito Fire has scorched 120 square miles (310 square kilometers) and was 85% contained as of Monday.

The fire in the Sierra Nevada foothills, about 110 miles (180 kilometers) northeast of San Francisco, broke out Sept. 6 and has destroyed at least 78 homes and other structures and charred forestland across Placer and El Dorado counties.

Earlier this month, the fire surpassed the size of the previous largest conflagration in 2022 — the McKinney Fire — although this season has seen a fraction of last year’s wildfire activity so far. Fire officials said total containment of the Mosquito Fire is expected around Oct. 15.

PG&E is cooperating with the U.S. Forest Service investigation, which has yet to determine what caused the fire, the utility said in a statement Monday.

The utility said it is conducting its own investigation into what sparked the fire and that it doesn't have access to the physical evidence that was collected by the Forest Service investigation over the weekend.

“As the threat of extreme weather continues to impact our state and the West, we remain focused on preventing major wildfires and safely delivering energy to our customers and hometowns," it said.

PG&E equipment has been blamed for several of California’s deadliest wildfires in recent years, even as drought and heat waves tied to climate change have made wildfires fiercer and harder to fight.

The utility pleaded guilty in 2019 to 84 counts of involuntary manslaughter for a 2018 fire ignited by its long-neglected electrical grid that nearly destroyed the town of Paradise and became the deadliest U.S. wildfire in a century.

PG&E filed for bankruptcy protection in 2019, after that fire and others were blamed on its aging equipment. The utility emerged from bankruptcy in 2020 and negotiated a $13.5 billion settlement with some wildfire victims. But it still faces civil and criminal actions related to other fires.

On Friday, a lawsuit claiming the Mosquito Fire was ignited by PG&E’s poorly maintained utility infrastructure was filed in San Francisco Superior Court.

“The damage done to several counties by PG&E was entirely avoidable with their knowledge and expertise as electrical service providers,” attorney Gerald Singleton said in a statement.

“PG&E continues to act negligently and has been responsible for more than 1,500 fires across the states leading to deaths, property destruction, financial burdens, and ruined lives because of their poorly maintained utility equipment,” Singleton said.

The financial impact has not yet been reported but will likely be significant due to the number of acres that have been charred and recklessly ruined, forever changing the communities and lives of those affected, Singleton said.