Portland, Sep 13 (IANS): Seven people have been confirmed dead, while dozens remain unaccounted for as historic wildfires continue to rage throughout the US state of Oregon, officials said.

The fires have scorched more than 1 million acres throughout the state, reports Xinhua news agency.

The figure is about twice the yearly average over the past 10 years, according to a report by OregonLive.

The blazes have caused widespread evacuations, forcing more than 40,000 to flee their homes.

Many evacuations remain in effect Saturday, while some have been downgraded.

Air quality of Oregon's largest city of Portland was the worst across the world on Saturday morning because of the fires.

The National Weather Service's Portland office said air quality will likely remain poor through the weekend.

Health experts have advised all residents to stay indoors unless absolutely necessary.

Oregon fire officials are also dealing with the 130,000-acre Riverside Fire at 0 per cent containment and Lionshead Fire at 138,000 acres and just 5 per cent containment.

Meanwhile, the Oregon State Police on Saturday announced Fire Marshal Jim Walker had been put on paid leave.

Mariana Ruiz-Temple, Chief Deputy State Fire Marshal, has been appointed the acting fire marshal.

"Mariana is assuming this position as Oregon is in an unprecedented crisis which demands an urgent response," Travis Hampton, the state police superintendent, said in a statement.

"This response and the circumstances necessitated a leadership change," he added.

Besides Oregon, massive wildfires were also raging in California, Washington, Colorado, Idaho and Utah.