(AP) – In a long-awaited report, state investigators said Thursday that a 2017 wildfire that killed 22 people in Northern California wine country was caused by a private electrical system, not equipment of embattled Pacific Gas & Electric Co.

The state’s firefighting agency concluded that the fire started next to a residence. The agency did not find any violations of state law.

“During my investigation, I eliminated all other causes for the Tubbs Fire, with the exception of an electrical caused fire originating from an unknown event affecting privately owned conductor or equipment,” wrote CalFire Battalion Chief John Martinez.

Details about the property were blacked out in the report.

The fire was one of more than 170 that torched the state in October 2017. It destroyed more than 5,600 structures over more than 57 square miles (148 sq. kilometers) in Sonoma and Napa counties.

The cause came as a relief to PG&E, which plans to file for bankruptcy protection next week, citing billions of dollars in potential damages and lawsuits it faces from other deadly wildfires for which it has been determined to be at fault.

One witness reported seeing a transformer explode. Another reported seeing the fire approach a PG& E power pole.

One witness, Charlie Brown Jr. of Calistoga, said the electrical wiring leading from the property where investigators concluded the fire started had not been used in years.