Trees are engulfed in flames in Colorado's High Park Fire, about 15 miles (24 km) northwest of Fort Collins

REUTERS

A lightning-sparked wildfire that has engulfed scores of buildings and left one person missing roared unchecked for a third day through the Colorado mountains north of Denver on Monday, and hundreds of residents remained evacuated, reports Reuters.

Fuelled by tinder-dry vegetation and fanned by erratic winds, the so-called High Park Fire nearly doubled in size, leaving 57 square miles (147 sq km) of timber and grasslands blackened northwest of Fort Collins, Colorado, near the Wyoming border, said Larimer County Sheriff's spokesman, Nick Christensen.

Hundreds of miles to the south in central New Mexico, firefighters raced to the southern flank of a separate wildfire burning out of control in the Lincoln National Forest as flames crept closer to the resort town of Ruidoso.

About 1,500 people fled over the weekend from several communities on the northern and western fringe of the New Mexico blaze, dubbed the Little Bear Fire, officials said.

That fire, also caused by lightning, was burning in the same area where firefighters in 1944 rescued the orphaned bear cub that became known as "Smokey Bear," a symbol of the U.S. Forest Service and the government's fire-prevention campaign.

"We have 13 types of aircraft in the air, and we're hitting it with everything we have to keep it from the village of Ruidoso," said fire information officer Sean Parker.

In Arizona, authorities reported a firefighter lost his life on Friday when the vehicle he was riding in rolled over en route to a blaze in the Baboquivari Mountains west of Tucson.

Anthony Polk, who lived in Yuma and worked for the U.S. Bureau of Indian Affairs, became the third member of a firefighting team to die in the line of duty in wild-land blazes that have scorched more than 1,400 square miles (3,625 sq kilometres)so far this year, mostly in Western states.

The pilot and co-pilot of a tanker plane were killed when their aircraft crashed last week in south-western Utah.

As of Monday, firefighters were battling a total of 17 large, uncontained blazes, most of them in eight Western states - New Mexico, Arizona, California, Colorado, Wyoming, Utah, Idaho and Alaska, according to the National Interagency Fire Centre in Boise, Idaho.

The High Park blaze in Colorado, at 37,000 acres (14,973 hectares) and growing, already has caused significant property damage and ranks as a top priority for U.S. fire managers.

At least 100 structures have been consumed, including an undetermined number of homes, and one person has been missing since the blaze erupted, Larimer County Sheriff Justin Smith said. That person lives in a neighbourhood where houses are known to have been destroyed, but hazardous conditions have prevented crews from conducting a thorough search of the area.

Firefighters reported flames consistently leaping 15 to 20 feet (4.6 to 6 metres) in length, with some 300-foot-tall flames arcing from treetop to treetop as the blaze advanced at the rate of about a mile an hour, Christensen said.