The California fires started on Monday, July 23 when a vehicle suffered mechanical failure, officials said.
Of 16 people reported missing, nine have been found, Shasta County Sheriff Tom Bosenko said yesterday.
Redding Police Sergeant Todd Cogle said communication issues were making it hard to contact people.
He said: “We spoke with several people who left their cell phones at their residences and in this day and age people don’t remember people’s phone numbers.”
Firefighters have been making progress trying to contain the fire, but it began to spread quickly on Thursday night when it jumped across the Sacramento River, according to Reuters.
A red flag warning and heat advisory are in effect for the area until Monday at 8am local time.
The fire, in the Shasta County in northern California, has killed six people so far, including two children and their great-grandmother.
The deadliest blaze doubled in size over the weekend as two firefighters also lost their lives in an attempt to kill the fire.
Authorities said the latest victim had not complied with an evacuation order.
Sacramento firefighter Chris Harvey told local media: “This fire is a disaster.
“It’s a very large event with very high speed and very high temperatures that are going to last a couple of days.
“The fire still has very explosive behaviour.”
Fire in the Trinity/Shasta County now covers 95,368 acres and is 17 percent contained.
The fire is burning along Hwy 299 and Carr Powerhouse Road, Whiskeytown.
So far, the fire has claimed 657 homes, three businesses and 214 buildings, 175 buildings have been damaged and more than 5,000 structures are under threat.
More than 38,000 people in the Redding area were under evacuation orders on Sunday.
Chris Anthony, a division chief with the California Department of Forestry and Fire Protection (Cal Fire), said: “Under these conditions that we are seeing right now, it’s not going to take much for the fire to have the extreme spread that we saw a couple of days ago.
“We are simply not getting a break.”
President Donald Trump declared the fire an emergency on Saturday, authorising federal funds for disaster relief efforts.
More than 160 fire departments from across California and the country are working to tackle the inferno.