FLAGSTAFF, Ariz. --
Crews battling a 10,000-acre fire that has threatened hundreds of homes were sending planes Tuesday to learn the full scope of the blaze, which choked the skies with rolling clouds of smoke and sent flames high into the air.
About 10 percent of the wildfire outside Flagstaff was under control late Monday, as firefighters focused Monday on protecting endangered homes by digging trenches, clearing out dry brush and spraying them down.
At the height of the fire, rolling clouds of black and gray smoke darkened the sky north of Flagstaff, and bright red and orange flames shot up more than 60 feet in the air. The smoke lingered over roadways, forcing drivers to use headlights in daylight hours.
The flames reached the back yards of some homes while coming within a few hundred feet of others, said Dugger Hughes, the incident commander. No structures have burned.
"The homes are looking very secure right now," he said.
Hughes said crews would fly over the area early Tuesday morning to get a better idea of the perimeter and of spot fires, some of which have jumped up to a half-mile ahead of the so-called Schultz fire.
Residents of about 750 homes remained under evacuation orders, and Coconino County Sheriff Bill Pribil urged them to be patient.
"At this time we're not prepared to put people back in their homes," he said Monday evening.
Heat, low humidity and strong winds have challenged firefighters on the ground and in the air in the area northeast of Flagstaff. Sustained winds of up to 20 mph with gusts of more than 30 mph grounded heavy air tankers Monday.
The fire is believed to have been started by an abandoned campfire, and authorities were looking for anyone who might have more information. The fire is burning in rough terrain, consuming ponderosa pine, mixed conifer and dry brush.
Flagstaff, a mountain town of about 60,000, is a popular place for tourists and home to Northern Arizona University. A ski resort and snowfall lure visitors during the winter. Moderate summer temperatures provide an escape from more intense desert heat during the summer.
Areas just north of Flagstaff that are under evacuation orders are a mix of upscale, manufactured, ranch-style and second homes that sit at the foot of the mountains and beyond.
The fire also abutted U.S. 89, a key route to Grand Canyon National Park about 75 miles to the north, and officials remained concerned that high winds could send the fire across the roadway.
A federal management team took over direction of the firefighting effort Monday, a move that expanded access to resources. More than 800 firefighters were battling the blaze Monday.
The fire was the second that broke out in two days in the Flagstaff area.
Some of the residents of the 116 homes evacuated because of the earlier fire in southeastern Flagstaff were allowed to return home after crews worked to establish a perimeter around the 300-acre blaze. A California man was arrested on suspicion of starting that blaze by leaving behind hot coals at a campsite in a wooded area about two miles from downtown Flagstaff.
A third fire burning 11 miles northeast of nearby Williams is 60 percent contained after burning 3,420 acres.
Other wildfires in the West also kept firefighters busy.
In central Colorado, a wildfire that grew from at least five smaller blazes burned at least 700 acres Monday, destroying several structures and forcing the evacuation of homes, businesses and campgrounds near the Royal Gorge Park. Firefighters east of the Great Sand Dunes National Park in southern Colorado continued to battle a 4,700-acre fire burning amid high winds on rugged terrain.
In New Mexico, fire officials continued to make progress on two wildfires, including a fire that charred nearly 13,900 acres in inaccessible terrain in the Jemez Mountains.