The Gladiator Fire in Prescott National Forest near Crown King became the biggest fire in the state's 2012 wildfire season, growing to 16,240 acres Thursday, surpassing the Sunflower Fire, which burned 16,175 acres in Tonto National Forest, The Arizona Republic reported.
The red-flag warning of "widespread hazardous fire conditions" in much of the state was expected to be in effect from 11 a.m. Thursday until 8 p.m. Friday.
Sustained winds were expected to remain 20-30 mph with gusts as high as 50 mph Thursday.
High winds and low humidity fueled the Gladiator Fire, the only Arizona blaze to threaten communities, which has knocked out 17 power lines, destroyed six structures and led to the evacuation of four communities in Prescott National Forest. The fire was 30 percent contained.
Crews concentrated Thursday on the southwestern part of the fire where flames were threatening homes and communications towers.
Meanwhile, the Sunflower Fire, 30 miles north of Mesa, had burned 16,175 acres in Tonto National Forest and was 43 percent contained.
The Bull Flat Fire on the Fort Apache Indian Reservation had grown to 2,145 acres and was 95 percent contained while the Campini wildfire was burning in the Coronado National Forest, where it had consumed 60 acres and was 70 percent contained. The Elwood Fire, on the San Carlos Indian Reservation, was fully contained Wednesday after burning 1,600 acres.
In Nevada, smoke from the Topaz Ranch Estates fire near Wellington could be seen in the Las Vegas Valley and flowed into casinos in Las Vegas, the Las Vegas Sun reported.
The Clark County Department of Air Quality issued an alert Wednesday for increased pollutants in the air.
Dr. Joel Katz, director of the Allergy and Asthma Center in west Las Vegas, said the elderly as well as people with respiratory problems and cardiac disease would be most likely to be affected by the smoke.
Katz said people should avoid exercising outdoors and run air-conditioners when indoors or in their cars.