Brock Long, administrator of Federal Emergency Management Agency (FEMA), said the damage to Paradise was "one of the worst disasters" he had ever seen.
So far 48 people have been found dead in the Camp Fire that hit the town, but more than 100 more remain missing.
About 9,000 firefighters are currently battling wildfires across the state.
At a news briefing on Wednesday by officials, the director of California's fire service said "progress is being made" to contain the blazes.
"I want to just reiterate we continue to have a lot of work to do we will continue to be here, we will get this done until the job is over," Ken Pimlott said.