TALENT/EAGLE POINT, OREGON (REUTERS) - Dozens of extreme wind-driven wildfires burned through forests and towns in US West Coast states on Thursday (Sept 10), destroying hundreds of homes and killing at least nine people, authorities said.

In the past 48 hours, four people died from fires in California, while four were killed in Oregon and a 1-year-old boy died in Washington state, police reported.

Thousands faced evacuation orders in the three states.

Oregon bore the brunt of nearly 100 major wildfires ripping across the western states, with around 3,000 firefighters battling nearly three dozen blazes.

Police have opened a criminal investigation into at least one Oregon blaze, the Almeda Fire that started in Ashland near the border with California, Ashland Police Chief Tighe O'Meara said.

O'Meara said investigators were treating the origins of the Almeda fire as suspicious.

"We have good reason to believe that there was a human element to it. so we're going to pursue it as a criminal investigation until we have reason to believe that it was otherwise."

Police in Medford as well as in Douglas County to the north cautioned against rumours left-wing anti-fascists and right-wing Proud Boy arsonists were starting the fires.

The Oregon blazes tore through at least five communities in the Cascade mountain range as well as areas of coastal rainforest normally spared from wildfires.

In eastern Washington state a fire destroyed most of the farming town of Malden.

In central Oregon search and rescue teams entered torched communities like Detroit where firefighters led residents on a dramatic mountain escape after military helicopters were unable to evacuate the town.

A 12-year-old boy was found dead with his dog inside a burned car and his grandmother was believed to have succumbed after flames engulfed an area near Lyons, about 80km south of Portland, the Marion County Sheriff's Office said.

To the south, a Reuters photographer saw small communities near Medford, including Bear Lake Estates, reduced to ashes as he drove south on Interstate 5 towards Ashland.

Some people counted their blessings after fleeing the Bear Creek trailer park where nearly every house burned.

"Thank God we were at home," said Julio Flores, a resident of the community who escaped with two children who would have been alone had his restaurant working hours not been cut due to the coronavirus pandemic.

Firefighters said unusually hot, dry winds out of the east supercharged blazes, spreading flames from community to community, and then from house to house.

"When it really gets windy these embers are going for miles," said Firefighter Andy Cardinal in Eagle Point, north of Medford where the town of around 10,000 was on standby to evacuate.

Oregon Governor Kate Brown said up to 40,000 people had evacuated across the state where 364,217ha burned, dwarfing Oregon's average 202,342ha full-year total.

"We have never seen this amount of uncontained fire across the state," Brown told a news conference.

"We are feeling the acute impacts of climate change."

Climate scientists say global warming has contributed to greater extremes in wet and dry seasons, causing vegetation to flourish then dry out in the US West, leaving more abundant, volatile fuel when fires.

Firefighters expected two of Oregon's largest fires, burning around 38km southeast of downtown Portland, to merge.

Nearby Molalla, with about 10,000 residents was evacuated, and Canby, a community of 18,000 around 16km from central Portland, was told to be ready to leave.

Asked by a reporter whether Portland metro areas might be evacuated, Chief Deputy State Fire Marshal Mariana Ruiz Temple said she discussed such a possibility with local authorities and everything would depend on wind direction and force.

CALIFORNIA AND WASHINGTON FIRES

In California, officials said some 64,000 people were under evacuation orders while crews battled 29 major fires across portions of the most populous US state.

About a third of those evacuees were displaced in Butte County alone, north of the capital Sacramento, where the North Complex wildfire has scorched more than 99,957ha and destroyed over 2,000 homes and structures.

The remains of three victims were found in two separate locations of that fire zone, according to Butte County Sheriff Kory Honea, bringing the total death toll from this summer's devastating spate of California wildfires to at least 11.

Another person died in Siskiyou County in Northern California, state fire authority Cal Fire reported, providing no further details.

Wildfires have now burned over 1.2 million hectares in California in 2020, marking a record for any year, with six of the top 20 largest wildfires in state history occurring in 2020.

In Washington, a man and a woman were in critical condition with burns after their 1-year-old son died as they tried to escape the state's largest wildfire burning in mountains about 160km northwest of Spokane, the Okanogan County Sheriff's Office said in a statement.