The Palisades Fire, the largest wildfire to hit Los Angeles this week, may have been sparked by a New Year's Eve fireworks fire.

About 30 minutes after a wildfire alarm was sounded in the Palisades area northwest of Los Angeles on the morning of January 7, the city's fire department's radio system received information from the scene: "Fire broke out in an area very close to the New Year's Eve fire. It looks like this fire will spread very quickly."

Not long after, a firefighter called the operator to urge emergency reinforcements, warning that the fire was spreading very quickly to the neighboring urban area because of the many dry trees and bushes.

Within a week, the Palisades became the largest wildfire in the "fire triangle" surrounding the city of Los Angeles, in southern California. As of January 13, nearly 9,600 hectares (22,000 acres) had burned, with thousands of homes and forested land burned, while firefighters had contained only about 11 percent of the blaze, according to Reuters.

Los Angeles officials are investigating the cause of the Palisades wildfire. However, satellite imagery and accounts from residents in the area show that the fire broke out on January 7 on the same hillside where another fire was caused by people setting off fireworks to celebrate the New Year.

Margaret Stewart, a spokeswoman for the Los Angeles Fire Department, said local firefighters received a report of a fire in the woods northeast of the Palisades metropolitan area shortly after New Year's Eve.

A local resident told an investigator with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) that his family heard fireworks on the hill around 12:20 a.m. on January 1 and saw the fire erupt.

"A lot of people went into the woods to party at night, ignoring the warnings. They should have known better," the witness said.

The fire spread to about 1.2 - 3.2 hectares before being controlled by firefighters. At that time, the wind was not too strong and fire helicopters were quickly dispatched to the scene to spray water.

It took four firefighting teams about four hours to control the fire caused by fireworks. By 4:46 a.m. on January 1, the Los Angeles Fire Department concluded that the fire had been extinguished and would deploy forces to clean up the aftermath to "ensure the fire does not flare up again".

About six days later, when the dry Santa Ana winds returned, people discovered a column of smoke rising from the same Temescal hillside, in the Santa Monica Mountains, where the previous forest fire had occurred.

Satellite imagery taken at 10:45 a.m. on Jan. 7, about 20 minutes after videos of the Palisades fire went viral, shows a plume of smoke rising from the same area that burned on New Year's Eve and heading south.

Darrin Hurrwitz, a Los Angeles resident, said he smelled smoke while hiking around 9 a.m. at Skull Rock, at the base of the hill that burned early on Jan. 1, but he could no longer smell it when he reached the end of the trail.

Neighbors believe the embers from the New Year's Eve fire were not completely extinguished and flared up in the dry, low-humidity Santa Ana winds.

Don Griffin, who lives near Temescal Hill, captured images of the fire early on Jan. 1 northeast of the Palisades and on Jan. 7 captured images of the fire rekindling on the same hillside. The two photos show that the two fires appeared to have started very close together, according to experts.

“There’s no doubt that under these conditions, especially in dry weather, fires tend to smolder deep in the burned area. They’re unlikely to be completely extinguished, even with a soggy surface,” said Terry Taylor, a former fire investigator in California.

Alan Carlson, a former deputy fire chief for Northern California who has 50 years of experience investigating wildfires, said fires as small as 3 hectares (7 acres) in size are at high risk of rekindling. Strong winds earlier this week may have blown smoldering embers beyond the initial containment zone of firefighters.

"Looking at the two photos, I agree with the conclusion that these two fires are in the same area. It's hard to say for sure when I can't see what's happening on the other side of the hill, but the wind direction is consistent with the hypothesis that the first fire has rekindled," Carlson commented.

Some of the most serious wildfires in the history of the US West Coast also started from smoldering ash that was not detected and extinguished in time. Typically, the Oakland fire in 1991 killed 25 people, or more recently, the catastrophic wildfire on the island of Maui, Hawaii in 2023, devastated the town of Lahaina and killed at least 102 people.

In the summer of 2024, the California government also launched a propaganda campaign on social media, warning people that dry weather and low humidity could cause extinguished fires to rekindle. Fires can smolder in tree trunks or deep roots underground, even though the surface is no longer burning.