ESTACADA, OREGON (REUTERS) - Thousands of evacuees displaced by deadly wildfires across Oregon settled into a second week of life in shelters and car camping as fire crews battled on against the blazes and search teams scoured the ruins of demolished communities for those still missing.

With state resources stretched to their limit, President Donald Trump approved a request from Oregon's governor for a federal disaster declaration, bolstering US government assistance for emergency response and relief efforts.

Dozens of fires have charred some 1.8 million hectares of tinder-dry brush, grass and woodlands in Oregon, California and Washington state since August, ravaging several small towns, destroying thousands of homes and killing at least 34 people.

Eight deaths have been confirmed during the past week in Oregon, which became the latest and most concentrated hot spot in a larger summer outbreak of fires across the entire western United States. The Pacific Northwest was hardest hit.

The conflagrations, which officials and scientists have described as unprecedented in scope and ferocity, have also filled the region's skies with smoke and soot, compounding a public health crisis already posed by the coronavirus pandemic.

Satellite images showed high-altitude plumes of smoke from the fires drifting as far east as New York City and Washington, DC, carried aloft by the jet stream.

The fires roared to life in California in mid-August, and erupted across Oregon and Washington around Labour Day last week, many of them sparked by catastrophic lightning storms and stoked by record-breaking heat waves and bouts of howling winds.

Weather conditions improved early this week, enabling firefighters to begin to make headway in efforts to contain and tamp down the blazes.

The California Department of Forestry and Fire Protection (CalFire) said 16,600 firefighters were still battling 25 major fires on Tuesday (Sept 15), after achieving full containment around the perimeter of other large blazes.

Firefighters in the San Gabriel Mountains just north of Los Angeles waged an all-out campaign to save the famed Mount Wilson Observatory and an adjacent complex of broadcast transmission towers from flames that crept to within 152m of the site.

RECORD ACREAGE LOSSES

At least 25 people have perished in California wildfires over the past four weeks, while more than 4,200 homes and other buildings have gone up in smoke, CalFire reported.

Nearly 1.2 million hectares in California alone have burned so far - more than in any single year in its history - and five of the 20 largest wildfires on record in the state have occurred during that time frame.

One wildfire fatality has been confirmed in Washington state, where some 400 structures have been lost. Roughly 400,000ha have been blackened in Oregon, double the state's annual average over the past decade.

Oregon's death toll was revised downward on Tuesday after medical examiners determined that two sets of remains were those of animals.

At the height of the crisis there, some 500,000 residents - at least 10 per cent of the state's population - were under some form of evacuation alert, many forced to flee their homes as swiftly advancing flames closed in on their neighbourhoods.

Over 1,700 structures, most of them dwellings, have been incinerated At last count, some 16 people reported missing by friends and loved ones remained unaccounted for in Oregon, state emergency management officials said.

Last week, authorities said they were bracing for the possibility of "mass-casualty"incidents as search teams began to comb through the wreckage of homes destroyed during chaotic evacuations.

In the fire-stricken south-western Oregon town of Phoenix, uprooted families, many with young children, were sleeping in their cars and taking shelter at a civic centre or in churches, City Council member Sarah Westover said.

"It's much more difficult to follow the Covid restrictions given the environment," Ms Westover said.

Mr Marcus Welch, a food service director and youth soccer coach in Phoenix, said he had been helping a group of high school students whose homes were spared to run a community donation centre set up in a parking lot to assist evacuees forced from their mobile-home park, which was demolished.

"Every day, I hear a sad story. Every day, I hear a family displaced. People are crying because high school kids are giving them food, water. ... It's been a total blessing," Mr Welch said."Some people, they lost everything, so we encourage them to take everything they can."

Ms Westover said the community was in grief and shock, while fearing it might not be over. She and others who have evacuated still have their cars packed, ready to escape at a moment's notice, she said. Her house in Phoenix was spared, but others nearby burned down.

"It's like it cherry-picked - it burned down a house, then skipped two, then burned down another. I guess that's the way they kind of work with the embers flying around," Ms Westover said.

Local residents told of having to make quick getaways from fast-moving wildfires.

Ms Rhonda Johnston and Mr Chuck Johnston, of Gates, Oregon, described celebrating their 32nd wedding anniversary outside their RV playing card games and eating barbecued chicken in the parking lot of the Oregon State Fairgrounds after a hasty evacuation.

"This is something you never think you're going to go through," Ms Rhonda Johnston said. "We grabbed a couple days' worth of clothes, pills, and two cars full of pictures and two dogs and a cat and our daughter."