A firefighter searches for human remains November 16 in a trailer park destroyed in the Camp Fire.
CNN  — 

More than a week into three California fires, authorities are painstakingly searching for missing people and remains in ravaged neighborhoods.

Hundreds are reported missing, and dozens confirmed dead. Here are questions and answers about the search process.

Are all the people actually missing?

That isn’t clear.

Authorities are working from a list of people whose loved ones have called in “welfare checks” or reported them missing, Butte County Sheriff’s Investigations Sgt. Steve Collins said. After a call, officers go out to see if the home or other structure is still standing, or if the caller has heard from the missing person since.

Rescue workers sift through rubble in search of human remains in Paradise.

The process is made more difficult, Butte County Sheriff and Coroner Kory Honea said, by communications difficulties.

“There are a lot of people displaced (who) don’t know we are looking for them,” Honea said.

If people find their own or loved ones’ names on the list at the Butte County Sheriff’s Office’s website, they should call the sheriff’s office, Honea said.

Are the people unaccounted for mostly seniors?

The list of the missing includes people of all ages. But it also has a lot of seniors, with one as old as 101.

The hardest-hit town of Paradise has 27,000 residents, many of them retirees. An initial report showed almost all the homes were destroyed.

“I’ve never been to an incident with this much destruction and the complexity that’s tied to it,” says Dave Russell of Cal Fire, the state’s forestry and fire protection agency.

Do officials have a firm death toll?

The number of fatalities from the fires has gone up almost daily.

Many factors make it difficult for officials to reach a firm death toll. One, according to Collins, is simply that so much area remains to search.

“It’s the number of homes, the number of trailers, the multistory buildings,” Collins said. “All of that changes the complexity of this operation.”

The search continues at a trailer park destroyed by  the Camp Fire.

And once authorities know they have found human remains, they reach another obstacle identifying the victims.

Honea has invited relatives of the missing to visit the sheriff’s office in Oroville, so authorities can collect DNA samples to help identify victims.

How do they know who to look for?

The chaos left by the deadliest fire in California history makes it especially difficult to account for the huge populations affected.

Authorities will return to places they have searched to access new locations and to be as thorough as possible.

“We are going to continue searching because there are a lot of people that want some answers,” Collins said. “They are depending on us to find their loved one.”

CNN’s Hollie Silverman, Nicole Chavez, and Steve Almasy contributed to this report.