KACHINA VILLAGE, Ariz. -- Hundreds of firefighters worked Thursday to protect communities on the edge of Flagstaff from a wildfire that is chewing up a scenic Arizona canyon with towering flames and burning entire trees down to nothing but ash.
The human-caused Slide Fire started Tuesday and had burned more than 11½ square miles in and around Oak Creek Canyon, a scenic recreation area along a highway between Sedona and Flagstaff that normally would be teeming with tourists as the Memorial Day weekend approaches.
There were no reports so far of injuries or structures burned, although the fire grew tenfold from Wednesday and from 7½ square miles earlier Thursday.
Fire incident commander Tony Sciacca said Thursday night that crews have made good progress and some containment was expected to be announced by Friday morning, but he added, "We are not out of the woods yet."
The fire still was 3 to 3½ miles away from the residential areas of Forest Highlands and Katina Village, where 3,200 residents remained under pre-evacuation warnings.
Officials were mindful of the fire's dangers, as they looked at giant flames shooting up the walls of the canyon and saw how hot the fire was burning in the tinder-dry drought conditions.
"The fuels are just so dry, entire trees are turning to ash," said Dick Fleishman, a spokesman for fire managers.
A primary focus of firefighting efforts will be to pinch off the fire where it has reached the top of the canyon's northeast corner to keep it from burning northward toward residential areas, he said.
Sciacca said 500 firefighters were assigned to the fire Thursday, with an additional 200 personnel expected later in the day as more crews and engines arrive.
Firefighters are also taking extra steps to make sure they don't lose communication with crews in the steep canyons. They brought in "repeaters" that look like 20-foot-tall antennas and placed them on overlooks to maintain radio contact with firefighters below. Radio communication issues were a problem last year in a fire in nearby Prescott that killed 19 firefighters who were part of a Hotshot crew.
"If the fire makes any unfavorable movement, we know about it and I can alert them," said firefighter Rich Sack of the Carson Hotshots in Taos, New Mexico, as he held a radio and intently kept an eye on the fire.
The weather may help even as winds picked up Thursday afternoon with the prospect of higher humidity and a chance of rain by Friday, Fleishman said. However, he warned that thunderstorms could bring much-needed rain and moisture to dampen the blaze, but also lightning strikes that could start additional fires and powerful downdrafts that could push the blaze erratically in all directions.
"That's what happened with the Prescott guys last year," he said.
As smoke billowed over their homes, many residents of Kachina Village and Forest Highlands got out of town Wednesday rather than wait for an evacuation order. They filled their vehicles with clothes, heirlooms, medication, legal documents and family pictures.
Residents also cleared brush away from their homes and hosed down the landscape. Search and rescue crews with the Coconino County Sheriff's Office were going door to door while pre-evacuation warnings were in place. For those who they knew were safe, they placed a yellow ribbon on their mailboxes.
"I'm a Korean War veteran. There's not much that worries me," said 82-year-old Dick Summit, who decided to leave town and arranged to stay with a friend in nearby Flagstaff.
The fire has closed the main road between Sedona and Flagstaff. It's burning near Slide Rock State Park, a popular recreation area because of its natural rock water slides.
The fire forced the evacuations of 100 threatened businesses and homes in a 2-mile stretch north of the state park.
The fire has sent up large amounts of smoke and ash and created hazy conditions in Flagstaff, about 15 miles away. Health officials are urging people who smell or see smoke from the fire to curtail outdoor activity.
In southern Arizona, a wildfire on the Tohono O'odham Indian Reservation was fully contained Thursday after charring more than 200 acres. The fire southwest of Tucson was reported Tuesday night. Officials say no structures were damaged and no residents needed to be evacuated.