REDDING — Two young children and their great-grandmother are the latest victims of a massive and fast-moving wildfire in Shasta County that officials acknowledged Saturday they were making little progress in controlling.

Melody Bledsoe, 70, and her great-grandchildren, Emily Roberts, 5, and James Roberts, 4, died when their Redding home burned Thursday night, their family said. The death toll from the blaze known as the Carr fire stands at five with more than a dozen other residents reported missing.

With the unyielding 100-plus degree temperatures and bone-dry vegetation, authorities said there was no end in sight to the fire and expressed particular alarm about its rapid expansion. Between Friday night and Saturday morning, the fire doubled in size to more than 80,000 acres with only 5% containment. Despite the efforts of 3,400 firefighters aided by bulldozers and helicopters throughout the day, the blaze continued spreading toward residential areas west and south of downtown Redding.

“We understand the anxiety you are going through,” Shasta County Fire Chief Mike Hebrard told the community at an afternoon briefing. “We are doing everything in our power to bring an end to this chaos.”

The deaths of Bledsoe and the Roberts children underscored one of the fire’s most devastating features — speed.

Bledsoe’s granddaughter Amanda Woodley confirmed the news about their deaths Saturday afternoon in a public Facebook post written just after she left the Shasta County Sheriff’s Office.

Woodley said Bledsoe did everything she could to save the children.

“She was hovered over them both with a wet blanket,” she wrote.

“My heart is crushed,” she said. “I can’t believe this is real. I just keep seeing all of their beautiful faces.”

Bledsoe and her two great-grandchildren were reported missing late Friday by a family friend. They hadn’t been seen since their Redding home burned Thursday night.

Bledsoe’s husband, Ed Bledsoe, wasn’t home when the fire struck, according to an online fundraiser site created by another family member.

The family did not believe their home was under evacuation, and Ed went out to get supplies. The family was renting and did not have insurance.

According to news reports, the children called their great-grandfather while he was at the store saying the fire was approaching.

Speaking to the Sacramento Bee, Ed Bledsoe wept as he recounted trying to get back to the house.

“God almighty, I don’t know what I done wrong,” he said. “I talked to them until the fire got them.”

Shasta County Sheriff Tom Bosenko said no bodies had been found yet, but his investigators are “overwhelmingly sure that there are decedents at the scene.” He said access to the home has been difficult as the walls collapsed during the fire.

The fire, started Monday by a vehicle mechanical failure on Route 299, previously claimed the lives of Redding fire inspector Jeremy Stoke and bulldozer operator Don Ray Smith.

In responding to questions about the Bledsoe family’s fate, the sheriff implored residents to promptly obey evacuation orders.

More than 38,000 people have been displaced due to the mandatory orders.

The sheriff said 260 National Guard soldiers called into the area Saturday will help staff roadblocks to keep residents from danger and assist local law enforcement in ensuring those ordered to leave do so.

Authorities are investigating 13 other missing persons cases connected to the fire. Redding police Sgt. Todd Cogle said that there are indications that some reported missing are safe. When officers went to their addresses, he said, they found homes still standing and doors locked. In some cases, he said, people may have fled their homes without cellphones and might be unable to connect with relatives.

“My hope is that we are able to find all of them eventually, however, the possibility does exist that there may be far more grave situations for some of them,” Cogle said.

In addition to the human cost, at least 500 homes and other structures have succumbed to flames, authorities said. High winds are driving embers beyond the fire lines and igniting roofs and trees.

Near midday Saturday, firefighters patrolled Placer Road for small fires. The flames had already reached Vietnam Veterans Memorial Bridge, which spans Clear Creek in rural Igo. The fire left the bridge “compromised,” the California Highway Patrol said.

Evacuees filled the region’s hotels as well as several facilities set up by the Red Cross.

An evacuation center at Shasta College in Redding reached capacity before 9 a.m. The 500 people bunking down in the campus’ cafeteria and gymnasium included residents of three senior care facilities, many of whom are not mobile, said Peter Griggs, the college’s director of marketing and outreach. The campus is east of the 5 Freeway and “at a very safe distance,” he said.

On Saturday afternoon at Alta Mesa Elementary School, dozens of evacuees sat on folded chairs and bleachers in the school’s gym, listening to updates from fire officials during a town hall meeting.

Unified Incident Cmdr. Chief Brett Gouvea told them the fire had grown on multiple fronts. He said in five days the Carr fire had burned through the footprint of at least five major wildfires in the last 50 years in Shasta County history.

“I’ve never seen anything like that happen,” Gouvea said.

Ricky Young, incident commander for the National Park Service, said several wildfires burning across the state made it difficult to throw additional resources at the Carr fire.

As a result, the state has requested assistance from other agencies outside of California. He said about 150 engines were en route to help battle the huge blaze.

Attending the town hall meeting was Lance Starin, 60, who recently purchased property in Redding. He said his home was not in danger and that he came to the meeting to offer it as a shelter for families who may be looking for a place to stay.

Starin said he was impressed with the number of top-level fire officials who attended the meeting.

“I think it was brilliant to bring the commanders,” he said. “It shows they are united.”

Signs of the fire were unavoidable throughout the region. Ash rained onto the heads of fire officials during another midday presentation to evacuees.

Before taking questions, Sacramento firefighter Chris Harvey warned them that no one could answer the question on everyone’s mind: When can we go home?

“This fire is a disaster,” Harvey said. “This fire still has very explosive behavior.… It’s likely to continue that way.”

There was sporadic looting of evacuated homes, Redding Police Chief Roger Moore said. Patrols had stopped several suspects, he said, but made no arrests.

“We have an idea who they are,” said Moore, who lost his home earlier in the week.

One man crossing the evacuation lines was Jerry Kirk, a ferrier in Anderson. When the fire kicked up Thursday, Kirk wrote a Facebook post offering help evacuating livestock.

“I’ve had two or three hours of sleep since then,” Kirk said at noon Saturday.

With his Dodge pickup and a trailer, Kirk said he had rescued about 200 animals from rural ranches and farms, including 50 horses and numerous goats and sheep. Many times when he pulled onto a property, the flames were nearby and the residents and the animals panicked, he said.

“They aren’t going to leave their animals, and they are just waiting on me,” he said.

When he arrived in Igo to pick up animals at 5 a.m. Saturday, the fire seemed 10 miles in the distance, he recalled.

“Nobody was concerned or really moving that quickly,” he said. By his third trip, at 9 a.m., “there was fire right there in town.”

While this year’s fire season has already devastated California, it seems unlikely to relent, said climatologist Bill Patzert.

Several cities set all-time heat records this year — in July — but the most serious heat waves, Patzert said, typically don’t arrive until September.

“The dog days are not here yet,” he said. “We’re in for a long, hot summer.”

Or rather, many long, hot summers.

“The large picture, of course, is that we’re living in a warmer world. Temperatures are much higher this summer — next summer — than they were 50 or 100 years ago,” Patzert said.

And that heat sets a dangerous groundwork, said UCLA climate scientist Daniel Swain. Vegetation across much of the Golden State has already dehydrated to “explosively dry” levels not typically reached until September.

“It’s a lot easier to get bad fires under these conditions,” he said, “because you don’t need as much of a push from the winds.”

ruben.vives@latimes.com

harriet.ryan@latimes.com

Vives reported from Redding and Ryan from Los Angeles.

Times staff writers Andrea Castillo, Marisa Gerber and Alejandra Reyes-Velarde contributed to this report.