On Jan. 19, almost two weeks after the Eaton fire broke out near Altadena, Calif., technicians for Southern California Edison began testing electrical equipment near the origin of the blaze. They soon noticed small white flashes appearing on high-voltage transmission lines when power was being restored — signs that the system was functioning abnormally.

The incident is one of several irregularities that Edison has been reviewing as it examines its electrical system in the wake of the deadly fire, said Pedro J. Pizarro, president and chief executive of Edison International, Southern California Edison’s parent company, in an interview Wednesday.

He cautioned that the findings were part of the utility’s ongoing investigation and did not provide any conclusive evidence about whether faulty electrical equipment had ignited the blaze.

But the flashes, which could be similar to ones captured on video near electrical equipment just moments before the fire broke out on Jan. 7, add to a growing pool of evidence linking the utility to the possible origin of the fire, which killed 17 people and destroyed more than 9,400 homes and businesses.

It may take months for an official cause to be determined, but if Edison is found to be at fault, it could have sweeping consequences for how victims will be compensated — as well as how the utility, the state’s second-largest investor-owned utility, continues to operate.

“While we do not yet know what caused the Eaton wildfire, SCE is exploring every possibility in its investigation, including the possibility that SCE’s equipment was involved,” Mr. Pizarro said.

Edison filed its latest findings in a report to state regulators on Thursday.

In a separate filing Thursday, Edison said its equipment also might be associated with the Hurst fire, which began the same day as the Eaton fire and burned about 800 acres in the Sylmar neighborhood, north of Altadena.

Critics of the utility question why a comprehensive look at the cause of the Eaton fire took so long. They added that the mounting evidence suggested that the utility’s shareholders should be forced to cover the cost of damage from the blaze.

“Clearly Edison should have known that when you experience flashes on a line, that could cause a fire, in the exact place where the fire started,” said Jamie Court, president of Consumer Watchdog, a nonprofit group that represents taxpayers and consumers. “I don’t understand how they could not put two and two together.”
A spokeswoman for the California Public Utilities Commission said that the agency did not determine the cause of wildfires, but that it would review whether a utility violated any rules or regulations after it had been found responsible for causing a fire.

Utility equipment has been the source of some of California’s most deadly and devastating wildfires. After a series of blazes in the northern part of the state, including the Camp fire, which killed 85 people and destroyed the town of Paradise in 2018, Pacific Gas & Electric, the state’s largest utility, filed for bankruptcy.

For much of the last decade, California has worked to reduce wildfires set off by electrical equipment by requiring the state’s investor-owned utilities to develop prevention plans that have included moving wires underground, installing weather stations to track storms and even deliberately cutting power to customers during dangerous conditions.

As Edison began reviewing its data after the Eaton fire, it noticed that its system was under strain from 100-mile-an-hour winds that night, but it did not initially find any direct evidence suggesting its equipment was at fault.

The utility later expanded its internal investigation after The New York Times published a video recorded outside an Arco gas station in Altadena that captured flashes in the area of transmission towers in Eaton Canyon where the fire began on Jan. 7. The flashes occurred in short succession — one at 6:10 p.m. and then another three seconds later — before flames burst out below the towers.

“After we saw the video, we went back and said, ‘Hey, are there things we just don’t understand here, and we should bring back into the fold?’” Mr. Pizarro said.

The timing of the two flashes coincided with data released by Whisker Labs, a Maryland technology company that operates sensors in homes to help predict and prevent residential fires, that identified two huge transmission faults that originated in the Altadena area. The electrical disruptions were so strong that sensors registered the faults as far away as Portland, Ore., and Salt Lake City.
Edison said it was now looking at several factors that it initially had not considered relevant to the fire in Eaton Canyon, including electrical faults at 6:11 p.m. Jan. 7 on the transmission line near a substation several miles from the origin point of the Eaton fire.

It seemed a mystery, Mr. Pizarro said, that electrical problems so far from the origin point of the fire would play a role in igniting it.

The utility is considering whether an inactive transmission line might have sparked if electrified equipment nearby caused the line to energize. Mr. Pizarro said the utility had found signs of damage from arcing — when electricity jumps from one place to another and lines can dangerously flash and spark — on some inactive equipment. But, he added, it is unclear whether that damage occurred before or after the fire.

“What else happened in the system?” Mr. Pizarro said. “What else can we put together to try and concatenate some sequence of events?”