EDITOR'S NOTE: This story has been updated to correct the characterization of the state legislation.

Shares of Rosemead-based Edison International fell 12 percent on Nov. 12 after its utility subsidiary Southern California Edison announced that a problem with its transmission grid occurred near the point of origin of the massive Woolsey Fire now burning in Los Angeles and Ventura counties.

Also on Nov. 12, the San Jose Mercury-News reported that the California Public Utilities Commission has launched probes into both Southern California Edison and Pacific Gas & Electric – a unit of San Francisco-based PG&E Corp. – to assess whether the utilities complied with existing rules and regulations for their equipment in the current fire zones.

According to the Mercury-News and other press reports, Southern California Edison reported to the PUC that on the afternoon of Nov. 8 – the day the Woolsey Fire started – a circuit in its power transmission grid at its Chatsworth substation recorded a “disturbance” two minutes before the first report of fire came in from the Chatsworth area.

If the circuit disruption is determined to have sparked the Woolsey blaze, then Edison could be liable for all or most of the damages caused by the fire thanks to a peculiar state inverse condemnation policy and recent court and regulatory decisions. State wildfire legislation enacted in September – but not taking effect until Jan. 1 – will change this. After Jan. 1, Edison’s shareholder liability for damages resulting from the wildfires its equipment is found to have triggered will depend on findings from the PUC as to whether the utility was following existing rules and regulations regarding equipment maintenance and fire prevention.

As of mid-day Nov. 12, the Woolsey Fire had burned more than 91,000 acres in the eastern portion of Ventura County and the western portion of Los Angeles County, destroying or causing significant damage to at least 370 structures. Two deaths were being investigated to see if they were caused by the fire.

Edison shares plunged 21 percent to $48.30 within minutes of the market opening on Nov. 12, but regained nearly half of that loss by market close, ending the day down 12 percent to $53.56.

Education, energy, engineering/construction and infrastructure reporter Howard Fine can be reached at hfine@labusinessjournal.com. Follow him on Twitter @howardafine.