© David Sanders / AP
The Monument fire burns north toward Sierra Vista, Ariz., on Wednesday, June 15. Forty homes were destroyed or damaged three days into the fire.
Residents on the outskirts of Sierra Vista, Ariz., were told to evacuate Thursday, after 40-foot flames jumped a highway and high winds briefly grounded an air attack.

The wildfire in southern Arizona's Coronado National Forest is within 10 miles of Sierra Vista, population 40,000, and has destroyed or damaged at least 40 houses and 10 other structures over 14 square miles, or 9,500 acres.

Hundreds of residents in canyon areas outside the city had evacuated over the previous two days and more than 500 firefighters are attacking the blaze.

During the peak burning time Thursday afternoon, the fire is "probably going to look like a bomb went off," said fire information officer Dale Thompson. The next three days will be tough on the fire lines because of the winds gusting up to 40 mph, he said.

Officials on Thursday closed off a 12-mile stretch of State Route 92 due to the conditions. One county official driving along a still open section of SR 92 said he saw flames as tall as 40 feet on either side of the highway Thursday afternoon.

Winds and searing temperatures also were to move into New Mexico, where firefighters battling a blaze that surrounded Carlsbad Caverns National Park had it 70 percent contained and it was no longer threatening the park's visitors center and employee housing. The fire started Monday, charred about 30,500 acres of desert scrub and forced the park to close.

Interstate 25 reopened at 4 a.m. Thursday after being closed for four days because of the wildfire near Raton, N.M. However, Exit 454 in New Mexico and exit 2 in Colorado were to remain off limits Thursday because of the blaze burning on about 26,000 acres. Some nearby residents were able to return home Wednesday.

Arizona's Wallow fire, the largest in state history, grew again to 760 square miles, or 487,016 acres, as of Thursday morning, according to the U.S. Forest Service. It remained 29 percent contained, but fire managers are worried that expected gusts of up to 45 mph could put pressure on the eastern edge of the fire.

They're especially concerned about the fire burning in the Blue Range area south of Alpine. The least secure part of firefighters' lines and closest to the nearest town still threatened, Luna, N.M., where about 200 people live.

A nearly completed line of cut fuels and intentionally burned areas between Luna and the fire itself should be completed by Thursday morning, and fire commanders expressed confidence late Wednesday that it would hold.

"We feel we have enough room out there," said Jerome Macdonald, who leads one of three incident management teams assigned to the massive blaze. "We'll have a mile and a half burned out in front of it."

More than 4,600 firefighters are assigned to the Wallow fire.

A single campfire in the Bear Wallow wilderness was the fire's "most likely cause," said Apache-Sitgreaves National Forest supervisor Chris Knopp. He confirmed that investigators had questioned two people but declined to say any more about the investigation. He called them "persons of interest," not suspects.

When forest officials were first called to the fire May 29, they spotted a fire near a campfire, Knopp said. Officials also saw a separate fire about three miles away, but they were unsure if it had been sparked by the campfire, he said.

"I just hope they identify the people responsible for this," Knopp said.

Hundreds of firefighters have been working for days along the New Mexico line to keep the flames out of Luna. Thousands of others are working the rest of the fire, including around three mountain resort towns in Arizona.

Those residents still under evacuation could be allowed to go home by the weekend, Macdonald said. Alpine and Greer are under little fire threat now, but dangers such as burned trees that would topple must be removed before the area is reopened.

About 2,400 people remain evacuated from Alpine and Greer and smaller vacation enclaves after about 300 were allowed to return to the town of Nutrioso on Wednesday, said Brannon Eagar, the chief sheriff's deputy in Apache County. On Sunday, all 7,000 people evacuated from the towns of Springerville and Eagar were allowed to go home.

The blaze officially became the largest in state history on Wednesday when new mapping showed it exceeded the previous record-holder, the 2002 Rodeo-Chediski fire, which burned 732 square miles, or 469,000 acres, and destroyed 491 buildings. Though larger in size, the Wallow Fire has destroyed just 32 homes and four rental cabins. About 5,000 acres of it were burning in New Mexico.

Some questioned the Forest Service for not putting fire restrictions in place after a winter with well below-average snowfall and extremely dry conditions.

Asked about his decision, Knopp pulled out a picture of Springerville on May 19, after 6 inches of snow had fallen.

"It seems pretty foolish for the forest to implement fire restrictions when there was just snow on the ground," he said. "If I had it to do over again, I would probably do the same thing. If I had known a fire would start, I would do it differently."

Some in the region think differently.

Toby Dahl was evacuated from Escudilla, N.M., near the Arizona border and spent six days in a temporary RV park over 60 miles away in Pie Town, N.M. Fire restrictions should have been in place, despite the recent snow, he said.

Dahl, 62, said his place got only 11 inches of snow all winter, compared with nearly 80 inches last year.

"I don't have a degree or anything but I can tell you, you just don't let anybody into the forest under these circumstances," he said.

He wasn't sure what should happen to those responsible for igniting the blaze. But he said, "Something has to be done to make people think."

Teresa Shawver, 61, who lives on a small ranch in Quemado, N.M., said she would want the perpetrators to get "the max, whatever the law would allow," if the fire was set intentionally.

"If it was an accident, something got away from them, then I have a different view on that," Shawver said.

The fire was "terrible for everybody around here," she said. "But if it was just an accident, then that's what it was."

A third Arizona fire had burned 309 square miles and was 60 percent contained despite high winds and heat.

Elsewhere around the West Thursday, crews fought smaller fires near Yakima, Wash., Veyo, Utah, Westcliffe, Colo., and Fort Carson, Colo.

Fires have devoured hundreds of square miles in the drought-stricken Southwest and Texas since wildfire season began several weeks ago. And the outlook from 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.