Megan Janes says her aunt and uncle, Paradise residents Paula and Randy Dodge, are no longer missing but also "no longer with us". Officials set up three phone lines for loved ones to call and said they had to adjust to a new system of organizing the calls.
Janes adds that her "heart is quite heavy" but that "God will see us through".
At least three other people have died in southern California in another blaze dubbed the Woolsey Fire, which engulfed parts of Malibu, destroying the homes of several celebrities.
The firefighter is among the more than 100 firefighters from Washington state who have been sent to both Northern and Southern California to help with the deadly wildfires.
"The fact that we have thousands and thousands of people in shelters would clearly indicate that we were able to notify a significant number of people", the sheriff said.
The White House said on Thursday that President Donald Trump, who has been criticised as having politicised the fires by casting blame on forest mismanagement, plans to visit the fire zones on Saturday to meet with displaced residents.More news: Sarri makes Premier League history as Chelsea share points with Everton
The blaze has scorched 141,000 acres and destroyed 11,862 structures.
The revised official roster of 630 individuals whose whereabouts and fate remained unknown is more than double the 297 listed earlier in the day by the Butte County Sheriff's Office.
"It's cold and scary", said Lilly Batres, 13, one of the few children there, who fled with her family from the forested town of Magalia and didn't know whether her home survived.
Firefighting efforts have made progress in recent days, with the fire 52 percent contained. One body in Paradise was found in a auto that had been flipped on its side.
Meanwhile, hundreds of fire refugees are living in tents and makeshift shelters. "There are more evacuees, more people running out of money for hotels".
Ten search teams were working in and around Paradise - a town of 27,000 north of Sacramento.
Evacuation orders have been issued for the entire town of Malibu.