Show Low, Ariz. ? An explosive, 500-square-mile wildfire burned nearly to the doorstep of this evacuated mountain town Monday as ash rained down in an eerie shower on crews desperately fighting to hold back the flames.

The largest fire in Arizona history burned to within a mile of this town of 7,700 by noon. It had already destroyed at least 329 houses and 16 businesses, most of them in Heber-Overgaard, a community 35 miles west of Show Low that burned over the weekend.

Law enforcement vehicles approach a roadblock set up just outside of Show Low, Ariz. Monday's sky was smoky from the approach of an out-of-control wildfire.

Firefighters in Show Low faced two dire possibilities, depending on the weather: a wind-blown wall of flame that could overrun the town, or drifting embers that could start smaller fires across the community.

“There’s still a tremendous risk of fire jumping into Show Low,” fire spokesman Jim Paxon said, though winds were light and the fire was not the onrushing monster it was late last week.

President Bush planned to tour the area today.

Brown smoke spiraled into a hazy, gray sky Monday, and the sun cast a dull orange glow. Ash piled up in gutters and on cars. In neighborhoods nearest the fire, many homes with too much underbrush or wood shingles were marked with red flags to show there was no use trying to save them.

Outside the wood-shingled home of Becky and Dany Seymour, a sprinkler system sprayed the lawn as firefighting helicopters dipped giant buckets into a nearby lake. The Seymours had packed a trailer and their vehicles were ready to go.

“If we see flames, we’ll go, but we don’t know where we would go,” Becky Seymour said.

The blaze in dense pine forest on the edge of eastern Arizona’s White Mountains has charred more than 331,000 acres or 517 square miles, an area bigger than Los Angeles since it began as two fires last week. The fires merged Sunday.

Thousands flee

About 30,000 people have fled more than a half-dozen towns, including Show Low, 125 miles northeast of Phoenix. Show Low has been a virtual ghost town since Saturday, although a few residents like the Seymours have refused to leave.

Hoping to at least blunt the fire’s force, crews fortified a line bulldozed at a canyon just west of town and set backfires to remove fuel from the wildfire’s path. Firefighters also searched the town for spot fires.

“I think most of our businesses and homes are going to be saved. You have to think that way otherwise you’ll be in trouble,” said evacuated Show Low resident Mari Corella.

A large plume of smoke rises from southwest of Show Low, Ariz. The Rodeo wildfire remained outside city limits Monday, but burning embers and sooty ash fell throughout the town.

The community’s economy centers on tourism and recreation, along with forest products. The area, at 6,000 feet, is popular with outdoor enthusiasts and Phoenix-area residents who have built summer homes to escape the desert heat.

The town got its name when two 19th-century pioneers decided there was not enough room for both of them. They agreed to let a game of cards decide who was to move, with one telling the other: “If you can show low, you win.”

The wildfire has already overrun parts of the evacuated communities of Linden, Pinedale, Clay Springs and Heber-Overgaard.

The larger of the fires, the so-called Rodeo blaze, was believed to have been caused June 18 by people, though authorities do not know whether it was an accident or arson. The other was started Thursday by a lost hiker signaling for help.

Colorado fires continue

In Colorado, crews fought a 66,310-acre blaze that had destroyed 45 homes near Durango. The fire flared Monday, forcing dozens of residents from more than 100 homes. In all, some 1,200 homes have been evacuated.

South of Denver, a 137,000-acre blaze that had destroyed at least 133 homes was reported 69 percent contained. About 2,200 people had remained under evacuation orders until Monday night, when some residents in Teller County at the fire’s southern end were allowed to return. It wasn’t immediately known how many came back.

A firefighter who was injured last week in a van crash while en route to that blaze died Monday, bringing the death toll to five. Bartholomew Bailey, 20, of Corvallis, Ore., had been in critical condition since the accident last Friday.

Ranger’s claims doubted

An 18-year Forest Service veteran, Terry Barton, is charged with starting the blaze. Prosecutors allege Barton deliberately set the fire and staged the scene to look like a runaway campfire.

Her brother-in-law said during an interview Monday night on CNN’s new show, “Connie Chung Tonight,” that Barton told her family she burned a letter from her estranged husband and that the fire raged out of control.

“If the fire started because of her burning the letter, it was a total accident,” Lowell Freeman told Chung. Freeman is married to Barton’s sister, Carla.

Barton, 38, allegedly told authorities that she was so upset after reading the letter that she burned it. But investigators have said they found no evidence of burned paper at the fire’s origin and that her estranged husband, John Barton, has denied writing the letter.

Freeman dismissed speculation that Barton may have set the fire so she could put it out and look like a hero.

“She knows what the conditions are,” he said. “If you went and started a fire, you’d have to stomp it out right away.”

So far this year, 2.33 million acres have been burned by wildfires across the country, according to the government’s National Interagency Fire Center. The average for this time of year over the past decade is 948,000 acres.