Death toll in Redding climbs to five, as firefighters struggle to contain raging fire now into its fourth day.

Two children and their 70-year-old great-grandmother have died in northern California as a fast-moving wildfire raged into its fourth day, raising the death toll from the blaze to five.

Their bodies were found at a home destroyed on the outskirts of Redding in Shasta County, officials said on Saturday, as some 3,500 firefighters struggled to contain the erratic flames stoked by high winds and soaring temperatures.

Police say at least 17 people have been missing in the city of Redding since the blaze exploded into a firestorm on Thursday night, killing two firefighters, destroying more than 500 structures and forcing 38,000 people to be evacuated.

A vehicle problem ignited the blaze on Monday, but it wasn’t until Thursday that the fire exploded and raced into communities west of Redding before entering city limits.

On Saturday, it pushed southwest of Redding, the largest city in the region, towards smaller communities where scorching heat, winds and bone-dry conditions complicated firefighting efforts.

The Redding blaze is the largest fire currently burning in California and one of about a dozen major wildfires currently raging across the state.

Toys stand untouched near a home destroyed by the fire west of Redding, California [Bob Strong/Reuters]

With daytime temperatures expected to rise above 42 degrees Celsius over the next few days, there appears to be “no relief” in sight, said Al Jazeera’s Gabriel Elizondo, reporting from Redding.

“Under normal circumstances, the overnight hours serve as a reprieve, lowering the heat, giving fire crews a chance to get the upper hand, but this is no normal fire,” he said. “Strong winds after sunset have caused this fire to increase in size overnight, which is highly unusual.”

‘My kids are deceased’

The local Sacramento Bee newspaper said family members identified the dead as 70-year-old Melody Bledsoe, and her two great-grandchildren, James Roberts, four, and Emily Roberts, five.

The three were among more than a dozen people reported missing after the furious wind-driven blaze took residents by surprise and leveled several neighbourhoods.

The children’s mother, Sherry Bledsoe, was quoted by the newspaper as saying: “My kids are deceased, that’s all I can say,” as she left the sheriff’s office on Saturday.

Authorities also issued evacuation orders in Napa County when several structures caught fire, the Napa Valley Register reported. The blaze had blackened 60 hectares (150 acres) and was at 10 percent containment.

Throughout the state, Cal Fire officials said more than 10,000 firefighters were on the line, making progress on 14 large wildfires.

So far this year, wildfires have scorched almost 1.7 million hectares (4.3 million acres) across the country – less than last year – but still higher than the 1.5 million-hectare (3.7 million-acre ) average for the same period over the last decade.