As firefighters in Northern California have continued battling the country’s largest active fire, a new blaze raged Northern Colorado on Monday, prompting evacuations and causing unhealthy air quality alerts.

The Park Fire in Northern California has become the largest wildfire in the state so far this year and the sixth-largest in the state’s history.

The fire has consumed 373,357 acres (1,511 square km) across four counties.

The California Department of Forestry and Fire Protection (Cal Fire) reported that the blaze was 12 per cent as contained on Tuesday morning.

The fire’s rapid spread has been fuelled by abundant vegetation and one of the area’s hottest, driest summers on record.

The Park Fire’s destructive path also left 109 structures destroyed and five others damaged, with over 4,200 more under threat.

Authorities believed that the fire was deliberately set in a park near Chico last Wednesday afternoon.

A 42-year-old Chico resident has been arrested and charged with felony arson in connection with the incident.

California Governor Gavin Newsom had declared a state of emergency for the Park Fire and Gold Complex fires last week.

The latter, which started a week ago, has burned 3,007 acres and was over 98 per cent as of Tuesday, according to Cal Fire.

The Park Fire is currently the largest fire burning in the nation, surpassing the Durkee Fire in eastern Oregon, which has burned through 293,390 acres.

The massive firefighting effort involved more than 4,876 personnel, 33 helicopters and 434 fire engines.

Meanwhile, the Alexander Mountain Fire erupted in Northern Colorado on Monday morning near Roosevelt National Park and quickly grew to 864 acres by the afternoon.

The blaze’s rapid expansion has forced the evacuation of more than 2,600 people, with at least 1,500 receiving voluntary evacuation notices, according to the Larimer County Sheriff’s Office.

California is grappling with another significant wildfire, the Borel Fire in Kern County.

This blaze began on July 24 after a car caught fire during an accident, has already scorched 53,010 acres and had zero containment as of Monday. The fire’s swift advance through dry vegetation, exacerbated by hot, humid and windy conditions, has impacted several communities.

The widespread wildfires had threatened lives and property and severely impacted air quality across the Western U.S.

Smoke from the fires in Northern California and Oregon spread across several states, including Nevada, Idaho, Utah, Wyoming and Montana.

On Monday, the U.S. Environmental Protection Agency’s AirNow air quality data indicated the air was unhealthy for people with health issues in most wildfire-affected areas.

The National Weather Service’s Sacramento branch warned that the pollution would likely persist and potentially worsen as smoke settles into valleys where fires are burning. 

(Xinhua/NAN)