SPRINGERVILLE, Ariz (Reuters) - A massive wildfire that has displaced as many as 11,000 people in eastern Arizona held steady in size on Thursday, and fire officials said they hoped weaker winds and cooler temperatures would help them begin to contain the blaze.
But the Wallow Fire, which has charred at least 336,000 acres of thick, tinder-dry pine forest since erupting May 29, posed a new threat to power lines supplying electricity to Tucson, Arizona, some 200 miles to the southwest, and to El Paso, Texas, about 200 miles to the southeast.
The blaze, believed to have started from a campfire left unattended, cut through the popular White Mountains retreat of Greer on Wednesday, though fire crews managed to limit property losses there to six dwellings, said U.S. Forest Service spokesman Jim Whittington.
Although the Wallow ranks as the second-largest wildfire on record in Arizona, belching out palls of smoke that drifted across several states as far east as Iowa, no serious injuries have been reported. Property damage has been relatively light, with authorities reporting just 11 structures destroyed in all, at least four of them residences.
Greer, a mountain enclave of about 200 homes, was evacuated earlier this week when the wildfire initially crept close, then veered in a different direction.
Fire crews have so far kept flames from encroaching on two larger nearby towns of Eager and Springerville, which were ordered fully evacuated on Wednesday, though fire maps showed the leading edge of the blaze within a mile of Eager and within about 5 miles of Springerville.
The two towns are home to roughly 8,000 permanent residents combined, accounting for most of those displaced in the White Mountains region, a popular vacation destination for Arizonans seeking to escape the summer heat.
Governor Janet Brewer, who declared a state of emergency in two counties, put the total number of Wallow Fire evacuees at as many as 3,000 before Springerville and Eager were emptied.
Brewer said in a statement that she had spoken about the fire threat on Thursday with President Barack Obama, who she said "promised to provide as much federal support as needed to protect life, limb and property."
A handful of additional mountain hamlets west of Arizona's border with New Mexico have remained empty since their residents were ordered to leave days ago.
The easternmost flank of the blaze was still about a mile from the New Mexico line, and several small towns in that state have been placed on alert for possible evacuations.
Work continued on a bulldozed fire break stretching more than 10 miles into New Mexico, and Governor Susana Martinez ordered National Guard troops to the town of Reserve to assist in preparations for the blaze.
The firefighting force was increased by about a third on Thursday to more than 3,000 personnel, up from about 2,000.
Ground crews worked through the night with bulldozers to cut buffer zones between the fire's edge and populated areas and to set backfires designed to draw flames away from homes.
Their job was eased somewhat as the blaze began burning out of heavy timber into areas with fewer trees.
Dipping temperatures, rising humidity and calmer winds could also give firefighters a chance to begin establishing a firm perimeter around the blaze, which has engulfed well over 500 square miles in and near the Apache Sitgreaves National Forest.
"There's still potential for growth, but the weather is going to be much more conducive to firefighting," Forest Service spokeswoman Suzanne Flory told Reuters.
The latest aerial infrared images of the fire showed it had not grown in size during the past 24 hours, but rather appeared smaller than fire managers had estimated on Wednesday.
High winds that had rapidly spread the fire for several days also eased enough on Thursday to allow 22 water-dropping helicopters to resume their aerial assault on the monster blaze, joined for the first time by a DC-10 supertanker carrying a payload of fire retardant.
Adding a new dimension to the 12-day-old blaze was a warning from two utilities, Tucson Electric and El Paso Electric, that they might have to impose rolling blackouts if the blaze knocks out two large transmission lines that run through the fire zone.
The state's largest wildfire on record, the Rodeo-Chediski fire in eastern Arizona, blackened almost 469,000 acres in 2002 before it was snuffed.
Additional reporting by David Schwartz, Scott Disavino and Eileen O'Grady; Writing by Steve Gorman; Editing by Jerry Norton