A largely unchecked Colorado wildfire nearly doubled in size from Saturday to Sunday, prompting a fresh round of evacuations, with the blaze expected to grow in size as it is fuelled by bone-dry conditions and pushed by gusting winds, officials said.

The so-called 416 Fire in southwest Colorado had burned nearly 6,880 hectares by Sunday afternoon, an area larger than Manhattan. More than 800 firefighters were battling the blaze located north of Durango, which was 10 per cent contained, the Rocky Mountain Incident Management Team said.

The fire had burned about 3,640 hectares by early on Saturday, according to an aerial survey.

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A mandatory evacuation order was issued on Sunday for 859 residences, bringing the total number of homes under evacuation to about 2,000, La Plata County, Colorado, spokeswoman Megan Graham said.

Law enforcement officials were going door to door and residents have been warned to leave via calls to their phones, text message and emails, Graham said.

No structures have been destroyed so far, but the fire was a few hundred yards (meters) from homes with multiple aircraft dropping water and flame retardant to curtail the blaze, according to Inciweb, an interagency fire report.

“The terrain is rough and inaccessible in many areas,” the report said, adding June 30 is the estimated date for containment.

Low humidity and high winds have left firefighters bracing for the fire to spread and the weather was expected to be dry and windy on Sunday.

Images on social media showed large plumes of smoke disseminating above mountains against a backdrop of blue sky.

The National Weather Service has placed large portions of the so-called “Four Corners” region of Utah, Colorado, New Mexico and Arizona under a red flag warning of extreme fire danger due to the dry conditions.

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A blaze known as the Burro fire prompted U.S. Forest Service officials on Saturday to close part of the Colorado trail in the San Juan National Forest.

In addition, an air quality health advisory was extended on Sunday due to unhealthy levels of smoke, according to the Colorado Department of Public Health and Environment.

In 2017, a near-record 4 million hectares were burned in U.S. wildfires, the National Interagency Coordination Center said.