Video: Over 600 declared missing in California wildfire, death toll climbs to 63

As rescue operations continued on Friday as the wildfire raged in California, authorities said 631 people were listed as missing as the death toll continued to rise.

The number of missing in California wildfire has jumped past 600, Butte County Sheriff Kory Honea said. Earlier the authorities had said over 300 people were missing.

The sheriff informed that the number of those missing had more than doubled after authorities checked emergency calls when the wildfires first started over a week ago.

California authorities have taken DNA samples from relatives in order to identify those killed in the wildfire. At least 63 people have so far been killed as a result of the wildfire which has been the biggest in the history of the state.

"Beginning Thursday, anyone who believes a family member perished can provide a DNA sample," Honea said.

Meanwhile, the White House in a statement said President Trump would visit the state to review the situation. County town of Paradise in northern California has been worst hit by the wildfire with most of those missing reported to be in the age group of 70s, 80s and 90s.

A number of celebrities have lost their homes in Malibu including Gerard Butler, Miley Cyrus, Pierce Brosnan, Neil Young, Robin Thicke and Shannen Doherty.

California fire department had said that that the wildfire had destroyed 56,655 hectares but was only 40 per cent contained. At least 5,500 firefighters were battling the blaze.

Authorities, however, added that cooler temperatures had brought welcome relief to firefighting.

The cause of the deadly wildfire is still unknown although a lawsuit has been filed against the local power company, PG&E, by fire victims claiming negligence.

Authorities said it was unclear when residents would be allowed back into the town.