Wildfire reaches doorstep of Slow Low

An explosive 500-square-mile wildfire has burned practically to the doorstep of the evacuated US mountain town of Show Low, Arizona, as crews fought to hold back the flames.

The fire, formed from the convergence of two destructive blazes, had burned to within a mile of the town of 7,700 by last night.

Depending on the wind, firefighters could face two dire possibilities - a wind-blown wall of flame could overrun the town, or drifting embers could start smaller fires. By mid-morning, falling ashes lightly coated the town.

‘‘There’s still a tremendous risk of fire jumping into Show Low,’’ fire spokesman Jim Paxon said.

But the weather had improved, with winds of 10-15mph, about the same as on Sunday, when the fire’s advance slowed.

The blaze in dense pine forest on the edge of eastern Arizona’s White Mountains had charred about 331,000 acres 517 square miles since it began as two fires last week. The fires merged on Sunday.

About 30,000 people have fled more than a half-dozen towns, including Show Low, 125 miles north-east of Phoenix, which was evacuated on Saturday.

The fire had destroyed at least 329 houses and 16 businesses, officials said. Most of the destruction was in Heber-Overgaard, a community 35 miles west of Show Low that was overrun on Saturday.

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

The larger of the two fires that merged was believed to have been started on June 18 by people, though authorities do not know whether it was an accident or arson. The other was started on Thursday by a lost hiker signalling for help.

In Colorado, meanwhile, crews fought a 62,500-acre blaze that had destroyed 45 homes near Durango.

And a 137,000-acre blaze south of Denver has destroyed at least 133 homes. About 2,200 people remained under evacuation orders, down from 8,900 last week.

A doctor has concluded that Ann Dow, who died three days after the fire started, suffered a severe asthma attack brought on by smoke.

Ms Dow, 50, died of an asthma attack and smoke inhalation, according to her death certificate and her doctor. She collapsed on June 11 after telling her husband she could not breathe.