San Francisco, Sep 14 (IANS): Authorities confirmed that 10 people were killed, at least a dozen unaccounted for and hundreds reeling from lost homes due to the record-breaking wildfires across the US state of Oregon.

The fires have covered more than 1 million acres across Oregon, spanning from the southern border to the coast and Clackamas County. That figure is about twice the yearly average over the past 10 years, Xinhua news agency reported on Sunday.

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

The Jackson County Sheriff's Office said detectives had found all but one of the 50 people previously reported missing after the fire.

Oregon's fire marshal, Jim Walker, has resigned after being placed on leave, according to a Sunday report by the OregonLive.

The air quality of the state's largest city Portland worsened on Sunday morning, reaching 516 in parts of the city on the air quality index, according to the US Environmental Protection Agency.

The city was still ranked No. 1 in the worst air quality among major cities in the world by air quality monitoring website IQAir.com.