CHICO, Butte County — The number of people missing in the Camp Fire disaster jumped to 631 Thursday and officials said the death toll has risen to 63.

Butte County Sheriff Kory Honea delivered the grim news at a Thursday evening press conference, explaining that the list of missing skyrocketed after authorities did a comprehensive review of 911 calls and missing-persons reports.

Earlier in the day, authorities released an updated list of nearly 300 missing people. Honea noted that some people on the list may not be aware they have been listed as unaccounted for.

As he has done for several days now, Honea provided the latest information on remains that search crews have recovered: 7 additional human remains were found Thursday.

Two people were found in structures and one outside of a structure in Magalia. Three others were found in Paradise — two in a structure and one in a vehicle, Honea said.

Fifty-three of the victims have been tentatively identified, but authorities are waiting to confirm their identifications with DNA, Honea said.

People were encouraged to come to the Sheriff’s Office to give DNA samples. The death toll is expected to rise.

Investigators have discovered a possible second origin for the start of the Camp Fire, which is the deadliest and most destructive wildfire in California History, said Darren Read, a Unit Chief with Cal Fire.

Read declined to comment further on the second origin.

The cause of the fire remains under investigation and authorities are looking at whether it began with electrical equipment. On Thursday, no other information about the possible second origin was provided.

Fire officials have said that they believe the fire began at Pulga Road and Camp Creek Road near Jarbo Gap, just east of Paradise.

The Camp Fire has grown to 141,000 acres and has destroyed a total of 11,862 buildings, including 9,700 single-family homes. The fire remains 40 percent contained.

Sarah Ravani is a San Francisco Chronicle staff writer. Email sravani@sfchronicle.com