The deadly blaze that devastated the Altadena neighborhood in Los Angeles County early last year was ignited by a transmission tower belonging to the utility company Southern California Edison, fire officials said in a report released on Tuesday.
The county’s fire department said the blaze, which killed 19 people and destroyed more than 9,400 buildings, was started by electrical sparks coming off the tower, according to a joint investigation by the department and Cal Fire, the state’s firefighting agency. The tower was out of service at the time.
Though Edison had previously acknowledged that its equipment most likely started the blaze, known as the Eaton fire, the cause had not been officially confirmed.
Fire officials took 18 months to review evidence with experts, including video footage that showed “an unknown burning material” falling from the tower to the dry vegetation below in the Eaton Canyon area, according to the report. The blaze ignited about 12 seconds later, officials said, quickly spreading into surrounding neighborhoods.
The Eaton fire, which ignited on Jan. 7, 2025, raged through Altadena during a catastrophic week in which another blaze killed 12 people in the Pacific Palisades, bringing the total death toll from the Los Angeles wildfires to 31.
Together, the blazes were the second deadliest wildfire disaster in state history, behind only the Camp fire, which tore through Paradise, Calif., in 2018, killing 85 people.
Federal prosecutors have accused a man who they say harbored resentments against the wealthy of setting the blaze in the Palisades, an affluent neighborhood stretching from the Pacific Ocean to the Santa Monica Mountains. A Los Angeles judge declared a mistrial last month after the jury failed to reach a verdict. The man, Jonathan Rinderknecht, will be retried in October.
Many months later, thousands of destroyed houses in both Altadena and the Pacific Palisades are being rebuilt or are in the planning stages. Thousands of other buildings remain damaged by smoke, leaving many residents with no clear path to safely return home. The fires are estimated to have caused up to $164 billion in total property and other losses.
Anthony C. Marrone, the county fire chief, said in a statement on Tuesday that he recognized that no investigation could ease the pain of residents affected by the Eaton fire.
“While the cause has been determined, our focus remains on assisting our residents to rebuild their homes and livelihoods, and ensuring lessons learned drive meaningful and impactful change in memory of the 19 lives lost,” Chief Marrone said.
On Tuesday, Kathleen Dunleavy, a spokeswoman for Southern California Edison, acknowledged the findings.
“We have taken our potential role in the start of this fire seriously from the beginning,” she said. In a recent earnings call, company officials noted that their equipment was likely associated with the fire, she said, but they have also pointed out that wildfires of the Eaton fire’s magnitude “are rarely the result of a single factor.”
In October, the power company took the unusual step of establishing a compensation fund for victims even before fire investigators had determined the cause of the Eaton fire — a move that suggested that Edison had all but concluded that its lines had caused the blaze. It has committed hundred of millions of dollars in payments to victims.
The company has also filed lawsuits accusing government agencies and businesses of failing to warn residents of the fire and of not doing enough to prevent it from spreading.
For months, the utility and lawyers for customers had suspected that an inactive line might have been responsible for the Eaton fire. Even when out of service, the lines, sometimes referred to as “zombie” lines, can act as a conductor, picking up energy from active high-voltage lines nearby.
Investigators said that video footage obtained from a resident showed the moment the Eaton fire started, at about 6:11 p.m. on Jan. 7, 2025. The footage, they said, showed two bright blue and white flashes on the slope near the out-of-service tower, followed by an orange glow that appeared to be “dripping fire.” In interviews with investigators, several other residents described seeing flames under the tower.
Mikal Watts, a lawyer representing many Altadena residents who lost their homes, was among the people who had said earlier that an inactive power line may have been responsible for the fire.
“We are grateful that L.A. County took the time and the effort to review everything, and are pleased with its conclusions confirming our earlier work,” Mr. Watts said on Tuesday. “Edison must now pay for the $20 billion in damage it caused.”
