As the Palisades and Eaton fires continue to burn in Los Angeles County, experts say it could take weeks, months or even years for investigators to determine the cause of a couple of the most deadly and destructive wildfires in the state’s history.

The fires have killed at least 28 people combined, as investigators search for 22 others who are still missing. More than 17,000 structures across the Pacific Palisades and Altadena have been destroyed, according to Cal Fire and the Angeles National Forest. Damages from the fires could reach $385 million, with that amount expected to rise.

Rumors have circled around both fires, with some saying they heard fireworks in the area of the Palisades fire not long before it erupted, and videos claiming a Southern California Edison power line ignited the Eaton fire.

“It’s going to be long, arduous and there’s going to be hundreds of hours put into (investigating the fires),” said Glenn White, a retired fire captain from the Newport Beach Fire Department. “And I think they’ll have it locked down pretty well at the end.”

Wildfire investigations can be particularly time-consuming, as investigators must analyze sometimes thousands of acres in order to narrow down a specific point of origin. To determine a general fire pattern analysis, investigators observe the direction of burn patterns on each bush, rock or clump of grass found within the general area where the fire started, said Mike Cary, an arson investigator with the San Bernardino County Fire Department.

“You’re trying to narrow it all the way back down to either a single match or even a specific area,” Cary said, “which could be a couple feet in diameter or so.”

Fire investigators approach every case the same way, using the scientific method to help determine the origin and cause of a fire.

Before determining the cause, investigators have to find where the fire began by interviewing witnesses, reviewing 911 calls and satellite footage and scouring social media to find anyone who saw the blaze ignite, White said. While walking the fire line, investigators observe fire patterns, talk to crew members about what they saw when they first arrived on scene and search for the heel of the fire, or its point of origin.

It may be easier for investigators to find the point of origin in cases like the Palisades and Eaton fires, White said, because strong Santa Ana winds that helped the fires spread rapidly also likely blew the blaze in one direction from its heel. When winds are weaker, the fire spreads in all directions, making it more difficult to find where it started.

Once investigators know where the fire started, they rope the area off so that firefighters working the scene don’t tamper with any potential evidence. Then, the search begins for what ignited the blaze.

“When you have a wildfire,” said Ed Nordskog, a retired bomb and arson investigator with the Los Angeles Sheriff’s Department, “you have a ton of potential causes, and most of them are not arson.”

Strings, ropes and binoculars

Using strings, rope and nails, investigators set up a checkerboard-like grid and run magnets or metal detectors over each 2-foot by 2-foot square to find anything that may have started the fire, Nordskog said.

After that, they’ll break out binoculars or magnifying glasses to search for anything they may have missed.

“It looks sort of silly,” Nordskog said, “but there’s a person on their knees with binoculars, looking at the ground two feet in front of them. They’re looking for extremely small pieces of material that could have started the fire.”

If a wildfire occurred near a roadway, for example, it could be related to a catalytic converter failure, a brake fire, or a lit cigarette. Equipment or vehicles that cause a fire may leave behind extremely small pieces of metal.

Within the debris, investigators might find remnants of a match, firework, flare or other possible evidence of how the fire began. They search for anything that could have become hot enough to set fire to the fuel in the area, White said.

If investigators suspect power lines may have been an issue — like some have asserted in lawsuits against Southern California Edison in the Eaton fire — they might subpoena utilities for data or records that might show shorting or losses of power in specific areas ahead of the fire, White said.

During high winds, power lines might slap together, sparking hundreds of embers that leave certain patterns in the brush below and drop pieces of molten metal. Investigators may also subpoena the utilities to get the damaged lines themselves and bring them to electrical engineers, who will examine them, Nordskog said.

To determine if arson was a factor, investigators may ask if anyone tried to prevent crew members from reaching the fire or delay them from putting out the flames.

Eliminating potential causes

Cary will also ask about the fire’s appearance, how it reacted when firefighters attempted to extinguish it — and if there was anything odd about it.

“If there was any type of liquid involved with the initial cause for spread of the fire,” Cary said, “that will sometimes react differently.”

In those cases, applying water to the flame may cause it to grow or spread.

As they work, investigators try to eliminate all the potential causes that wouldn’t make sense for that particular wildfire until they narrow the search down to the likely causes, Nordskog said. Investigators then send fire debris to laboratories for their hypotheses to be tested, until they can pinpoint the exact cause of the fire.

Because of the loss of life and property, Nordskog expects fire investigators will take their time revealing any information about the cause of the Eaton and Palisades fires.

“They’re going to be very careful about releasing the cause of this for a while.”