Faulty wiring on a hot tub caused California's third-most-destructive wildfire, which left four people dead and destroyed more than 1,300 homes last year, California fire authorities say.

The Valley Fire burned 76,067 acres in the state's northern Sonoma, Lake and Napa counties last September. On Wednesday, investigators with the California Department of Forestry and Fire Protection revealed that a hot tub installed on a residential property in Cobb was the likely cause.

According to the agency's report, a copper wire overheated and sparked nearby brush. Investigators found that wiring on the hot tub was not up to building codes, and a permit for a structure housing the hot tub made no mention of any electrical work.

Homeowner John Pinch reportedly admitted to investigators that he installed the circuit. The San Francisco Chronicle says investigators concluded Pinch's actions "amounted to a misdemeanor, negligently starting a fire, and a building code violation for not having proper permits." The Chronicle further reports it's now up to prosecutors whether to file charges:

Lake County District Attorney Don Anderson, who learned only Wednesday of the state's findings, said he'll now look into whether a crime was committed and whether arrests would be made.

"First thing in the morning, I'll be turning this over to my investigative staff," he said.

Earlier Wednesday, before the results of the probe were made public, one owner of the home with the alleged electrical problem told The Chronicle that his property was not the cause of the fire, but that his two-story house had suffered minor damage — and that a toolshed near the alleged origin had burned.

'That shed was the victim of the fire,' said Parker Mills, who noted that when the blaze started no one was at the property on High Valley Road, a rural area marked by grassy hills and oak forest.

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