LUNA, N.M. >> Authorities expected a massive wildfire in eastern Arizona to become the state’s largest today, as investigators focused on two people whose campfire may have started the blaze and firefighters fought to keep the flames from devouring a small New Mexico mountain town.

Fires also grew elsewhere in New Mexico, including one near the Colorado border that forced the closure of a busy interstate highway.

Kelly Wood, a spokesman for the multi-agency effort battling the Arizona blaze, said late Tuesday that two people of interest were being questioned about an abandoned campfire but he didn’t immediately have details. He said the U.S. Forest Service would release more information Wednesday.

In Luna, N.M., just across the Arizona state line, evacuation plans were in place for the roughly 200 residents. Crews have been working to protect the town for days, hacking down brush, using chain saws to cut trees and setting small fires to burn anything that approaching flames could use as fuel.

Fires have devoured hundreds of square miles in the Southwest and Texas since wildfire season began several weeks ago. Scant winter precipitation in Arizona, New Mexico, part of west Texas and southern Colorado is blamed on La Nina, a term describing cooler waters in the equatorial Pacific Ocean that keeps the jet stream from dipping down and bringing storms to the region.

It instead sent rain and snow farther north, which has led to huge snowpack in the Sierra Nevada range in California and in the Rockies.

The wildfire outlook issued by the National Interagency Fire Center in Boise, Idaho, calls for fire potential to be above normal in those areas through September, but normal or less than normal across the rest of the West.

The huge blaze in Arizona was also made worse by the extremely thick forest, the result of a century of fire suppression that allowed additional tree growth in the world’s largest ponderosa pine forest. Fires that would typically scorch only grasses and small trees on the forest floor across the West now leap into the crowns and skip across miles of terrain through the treetops.

The Arizona fire has burned more than 747 square miles since Memorial Day weekend and destroyed 32 homes and four rental cabins. It was 20 percent contained.

Arizona’s largest fire was the 2002 Rodeo-Chediski fire, which burned 732 square miles but destroyed far more buildings — 491.

While the current fire has surpassed Rodeo-Chediski in size, it still wasn’t considered Arizona’s largest fire as of Wednesday morning because several thousand of the 478,452 acres that have burned were in New Mexico, where firefighters had intentionally set blazes to keep back uncontrolled flames, said Sean Johnson, another fire spokesman. Officials expected the blaze in the Apache-Sitgreaves National Forest, which is chewing up thousands of acres a day, to become the state’s largest by morning, he said.

“It’s just not there yet,” Wood added.

Although the fire is enormous, other U.S. blazes between 1997 and 2009 have been much larger.

The biggest was a 2004 blaze in Alaska that burned more than 2,000 square miles. The largest in the continental U.S. were a 2006 Texas blaze that consumed 1,417 square miles, followed by a 2007 Idaho fire that burned 1,018 square miles.

About 2,700 people who live in several Arizona resort communities in the forest remained evacuated from their homes. Wood said residents of the mountain town of Nutrioso would be allowed to return to their homes after 10 a.m. today, and fire officials said evacuation orders for the picturesque hamlets of Alpine and Greer might be lifted in several days.

Greer, considered the jewel of eastern Arizona’s summer havens, lost more than 20 homes and a couple dozen outbuildings as flames moved into the valley last week.

In northeastern New Mexico, a wildfire fanned by high winds has forced hundreds of people from their homes near the Colorado border and grown to more than 39 square miles. The blaze over more than 25,000 acres near Raton was burning on both sides of Interstate 25, closing the highway and sending summer motorists on lengthy detours. The fire has destroyed or damaged nine structures in New Mexico, including two houses. One cabin has burned in Colorado.

Another wildfire in southern Colorado spread to more than 3 square miles and forced the evacuation of a church camp. Residents of 50 homes were told to evacuate and another 50 warned to do so, Custer County Sheriff Fred Jobe said Tuesday.

Another fire in southern New Mexico had burned about 39 square miles near the Carlsbad Caverns and was threatening the visitor center and housing at the tourist destination.

Several other fires were burning around Arizona, including a huge blaze near the southeastern border town of Portal that has burned more than 267 square miles since May 8. It was about 60 percent contained. Another fire that broke out Sunday outside Sierra Vista near the Coronado National Memorial also forced evacuations.