TUCSON, Ariz. -- Firefighters lit controlled fires around homes, youth camps and an array of telescopes and antennas Friday as a windblown wildfire that already had destroyed 300 mountaintop homes threatened dozens more in gusting winds.
The Aspen fire remained a mile away from the closest structures Friday night. Firefighters struggled to deprive it of fuel should it make a run at developed areas spared by the wildfire's initial rampage across Mount Lemmon last month.
Driven by the wind, the fire ballooned from 41,500 acres on Wednesday to 68,000 acres Friday. It was 55 percent contained.
A gigantic cloud of smoke towered over Tucson as the fire blew across the Santa Catalina Mountains on Friday afternoon. Seven helicopters dropped water on the flames throughout the day.
Later, as Fourth of July fireworks exploded over the city, an eerie line of flame flickered above homes in the foothills on Tucson's northeast side.
Firefighters were helped Friday by a stiff wind from the northwest, which helped keep the fire moving eastward through steep terrain on the side of the mountain instead of pushing north up canyons leading to the mountaintop. With strong winds in the forecast again for Saturday, the areas were still considered threatened, said Dan Oltrogge, the incident commander.
"The fire is going to have great potential to get in there tomorrow," he said.
Fire crews conducted burnouts and thinned trees and other vegetation Friday around: Willow Canyon, with about 60 homes; Soldier Camp, which has about 50 homes; Mount Bigelow, home of an observatory and a group of antennas; and Organization Ridge, where several youth camps are located.
Hampered by smoke and wind, firefighters were unable to complete the burnout Friday around Willow Canyon, which was closest to the fire; they hoped to complete it in calmer conditions overnight, said Jerome Macdonald, operations chief for the firefighting effort.
The areas are southeast of the location burned when the fire destroyed 317 homes or cabins and seven businesses in and around the vacation hamlet of Summerhaven.
The fire also pushed toward the foothills of the Santa Catalina Mountains on the northeastern fringe of Tucson. It was within three miles of the visitor center of Sabino Canyon, a popular recreation area, and fire officials asked residents of about 50 upscale homes in the area to evacuate so fire trucks would have the roads to themselves.
Because of thin desert vegetation at the base of the mountains, the fire posed little threat to homes in the foothills, said Gail Aschenbrenner, a fire information officer.
Firefighters hoped to use Catalina Highway, the main thoroughfare uphill, as a firebreak, but the fire leaped across the road below the developed areas and kept moving east. Macdonald said crews would work overnight to try to establish lines at the head of that front.
The fire, which began June 17, was caused by a person. It has cost about $10 million to fight thus far, Oltrogge said.