LAS VEGAS, N.M. (AP) — Firefighters in northern New Mexico worked Monday in rugged terrain ahead of a massive wildfire, feverishly trying to position crews to clear brush and stop the monster blaze from burning more homes in the Rocky Mountain foothills.

The wildfire has charred 308 square miles (798 square kilometers) of tinder-dry ponderosa forests, making it the largest blaze burning in the U.S. during what has been an early start to the fire season. Thousands of people have been evacuated.

Much of the Southwest has been in the grips of drought for decades and warmer temperatures have combined with spring winds to make for dangerous fire conditions.

Crews in Arizona were dealing with strong winds Monday as they battled a fire near the U.S.-Mexico border that forced several dozen people from their homes.

And another wildfire in northern New Mexico near the federal government’s key facilities for nuclear research prompted Los Alamos National Laboratory and others in the area to begin preparing for evacuations, though officials stressed there was no immediate threat to the lab.

The fire has burned nearly 64 square miles (165 square kilometers).

Officials said some medically fragile residents and large animals already have been moved out of the area to lessen the traffic congestion should evacuations be ordered. They anticipated residents would have at least a day or two notice before being required to leave.

“If the fire gets its fifth gear, it will be here sooner than we want it to be,” said incident commander Rich Harvey. “We’re doing everything we can to check it.”

Strong, gusty winds continued to blow across the region after fanning the fires for weeks and often grounding essential aircraft used to drop water or fire retardant ahead of the flames, complicating efforts to contain them. Wind will continue to be a factor this week, along with low humidity, but to varying degrees depending on the day.

Fire officials predicted part of the main New Mexico fire would push north into rugged terrain that is difficult for firefighters to access.

“This isn’t a surprise to us. All the models showed this probably was going to happen,” said fire operations section chief Todd Abel, adding that crews have spent days working to protect ranch homes scattered thorough the area.

Nearly 1,700 firefighters were battling the blaze burning northeast of Santa Fe that was almost 50% contained. It has destroyed nearly 300 structures, including homes, commercial buildings and barns.

The region’s largest population center — Las Vegas, New Mexico, home to 13,000 people — remained largely safe from the flames after some area residents were allowed to return over the weekend. Schools were expected to return to in-person classes on Tuesday.

___

Montoya Bryan reported from Albuquerque, New Mexico. Associated Press writer Felicia Fonseca in Flagstaff, Arizona, contributed to this report.

Copyright © The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Follow @ktar923