A firefighter makes a stand in front of an advancing wildfire as it approaches a residence Saturday, July 28, 2018, in Redding ,Calif. (AP Photo/Marcio Jose Sanchez)

REDDING - California firefighters were gaining ground on Monday on a massive wildfire that has killed six people and destroyed hundreds of homes and businesses, while rescuers searched for at least seven people who were unaccounted for.

The Carr Fire ignited a week ago outside Redding, California, and doubled in size over the weekend, charring an area the size of Denver and forcing 38,000 people to flee their homes. Two firefighters and a woman, Melody Bledsoe, and her two young great-grandchildren are among the dead.

"I would've liked to have went in there and died with them," Ed Bledsoe, Melody Bledsoe's widower, said in a tearful interview with CNN aired on Monday in which he described his final phone call with his family as the flames closed in.

Centered 150 miles (240 km) north of Sacramento, the Carr Fire is the deadliest of the 90 wildfires burning across the United States. Collectively, wildfires have blackened 4.4 million acres (1.8 million hectares) of land so far this year, 21 percent more than the 10-year average for the time period, according to federal data.

The more than 3,000 firefighters battling the Carr Fire began to gain control of it on Sunday, cutting containment lines around 20 percent of its perimeter by Monday morning, according to the California Department of Forestry and Fire Protection (Cal Fire). For much of the weekend the fire was just 5 percent contained.

Firefighters were struggling to control the fire's western flank, where terrain is steep and the air thick with smoke, fire officials said.

"That's where we need to fly," Dominic Polito, of the Escondido Fire Department, said in a telephone interview. "We can still use helicopters, but we can't use the fixed-wing aircraft."

Gale-force winds that drove the fire late last week have eased to moderate speeds, but temperatures are again expected to top 100 Fahrenheit (37.8 Celsius), according to the National Weather Service.

The fire grew rapidly beginning on Thursday, confounding fire officials with the speed of its movement.

Nearly 1,000 buildings have been destroyed by the 99,000-acre (155 square mile) blaze, Cal Fire said. The fire leveled the town of Keswick, home to 450 people. It also sparked an effort to rescue people's horses and livestock in the rugged region, a popular fishing destination.

Some 260 National Guard troops and 100 police officers were stationed in evacuated neighborhoods to guard against looting.

Another California fire prompted a rare closure of much of Yosemite National Park last week, while a third forced mass evacuations from the mountain resort community of Idyllwild, east of Los Angeles.