By David Schwartz
PHOENIX (Reuters) - Fire crews battling stubborn flames in eastern Arizona's mountainous pine forests braced on Thursday for a return of stiff winds that could reverse gains against the largest wildfire in state history.
By daybreak, a force of more than 4,600 firefighters had managed to extend containment lines around nearly 30 percent of a blaze that has charred an area half the size of Rhode Island in and around the Sitgreaves-Apache National Forest.
Fire information officer Kelly Wood said much of the effort on the 19th day of the blaze would focus on holding fire lines steady and preventing flying embers from igniting new spot fires as winds grow in strength.
Weather forecasts called for more bone-dry conditions and sustained winds of 18 to 25 miles per hour, gusting to 45 mph, through Friday.
"It's a very important day on the fire," Wood told Reuters. "The winds are going to test the lines, and we'll just have to see what happens."
The so-called Wallow Fire has destroyed or damaged three dozen homes and displaced up to 10,000 people at its peak while roaring through 760 square miles of ponderosa pine forests in eastern Arizona near the New Mexico border.
The fire zone lies in the heart of the White Mountains, a picturesque area dotted with vacation cabins and popular as a retreat for Arizonans seeking to escape the summer heat.
The conflagration erupted May 29, apparently from a campfire left unattended in a thickly wooded stretch of the Bear Wallow Wilderness area, just east of the San Carlos Apache Indian Reservation.
U.S. Forest Service officials said on Wednesday two "persons of interest" were being questioned by fire investigators, but no arrests have been made.
On Wednesday, authorities allowed residents to return to the town of Nutrioso, one of several Arizona communities evacuated during the first week of the blaze. Two other towns, Alpine and Greer, may be given the all-clear by the weekend, depending on wind conditions, Wood said.
The New Mexico town of Luna, an enclave of about 200 people less than 10 miles east of the Arizona border, was still on alert for possible evacuation but appeared to be out of immediate danger.
The bulk of Arizona evacuees forced from their homes at the height of the fire were allowed back on Sunday when evacuation orders were lifted for 7,000 to 8,000 residents of Springerville and Eagar.
The latest aerial infrared images of the fire on Thursday showed that 487,016 acres -- or nearly 761 square miles -- have burned overall, surpassing the 468,638 acres charred in 2002 by the Rodeo-Chediski Fire in eastern Arizona. That makes the Wallow Fire the largest on record in Arizona.
The 2002 fire was far worse in terms of property losses, however, destroying 465 homes.
By comparison, the Wallow Fire has so far gutted 32 homes and damaged five others. Some three dozen nonresidential structures also have been lost. But no serious injuries have been reported.
(Writing by Steve Gorman; Editing by Greg McCune)