MORE THAN 1,000 firefighters backed by bulldozers and aircraft were battling the largest active wildfire in the US after strong winds pushed it across some containment lines and closer to a small city in northern New Mexico.

Calmer winds yesterday aided the firefighting effort after gusts accelerated the blaze’s advance to a point on Friday when “we were watching the fire march about a mile every hour”, said fire operations official Jayson Coil.

Ash carried 11km through the air had fallen on Las Vegas, and firefighters were trying to prevent the blaze from getting closer, said Mike Johnson, a spokesman from the fire management team.

But fire managers warned of windy conditions expected in the coming days, as well as impacts from smoke, and officials urged residents to remain vigilant for further possible evacuation orders.

Stewart Turner, a fire behaviour analyst with the fire management team, warned yesterday of a “very serious week” ahead due to the forecast winds.

More extreme fire danger was forecast for today for parts of New Mexico, Arizona, Nevada and Colorado, according to the National Weather Service.

Mapping imagery indicated that the fire which has burned at least 166 homes grew in size from 103 square miles (266 sq km) on Friday to 152 square miles (393 sq km) by early Saturday, officials said. The fire was described as 30% contained during a briefing yesterday evening.

Winds in northern New Mexico gusted up to 65mph (105kph) on Friday before subsiding as nightfall approached. By yesterday, aircraft that dump fire retardant and water were able to resume flights to aid ground crews and bulldozers.

The fire’s rapid growth on Friday forced crews to repeatedly change position because of threatening conditions but they managed to immediately re-engage without being forced to retreat, Coil said. No injuries were reported.

The fire started on April 6 when a prescribed burn set by firefighters to clear out small trees and brush that can fuel blazes was declared out of control. That fire then merged with another wildfire a week ago.

With the fire’s recent growth, estimates of people forced to evacuate largely rural areas plus a subdivision near Las Vegas doubled from 1,500 to 2,000 people to between 3,000 and 4,000, said Jesus Romero, assistant manager for San Miguel County.

Officials have said the fire has destroyed 277 structures, including at least 166 homes. No updated damage assessments were available on Saturday, Romero said.

Wildfires were also burning elsewhere in New Mexico and in Arizona. The fires are unusually hot and fast for this time of year, especially in the south-west, where experts said some timber in the region is drier than kiln-dried wood.

Wildfires have become a year-round threat in the West given changing conditions that include earlier snowmelt and rain coming later in the autumn, scientist have said.

The problems have been exacerbated by decades of fire suppression and poor management along with a more than 20-year megadrought that studies link to human-caused climate change.

In northern Arizona, firefighters neared full containment of a 30 square-mile (77 sq km) blaze that destroyed at least 30 homes near Flagstaff and forced hundreds to evacuate. A top-level national wildfire management team returned oversight of fighting the blaze to local crews on Friday.

National forests across Arizona announced that they would impose fire restrictions starting next Thursday which limit campfires to developed recreation sites and restrict smoking to inside vehicles, other enclosed spaces and to the recreation sites.