LAS VEGAS (Reuters) -- Fire crews hampered by wind gusts and the driest conditions in two decades in the U.S. Southwest made slow gains on Wednesday battling dangerous forest and brush fires, including a wildfire in Nevada that doubled in size overnight and destroyed 17 buildings and two homes.
Blazes in rugged, mountainous areas of Arizona, Colorado, Nevada, New Mexico and Utah have forced the evacuation of several small towns and torched more than 85 square miles (220 square km) of forest, brush and grass in the past two weeks.
No deaths or injuries have been reported in the fires, authorities said.
The Arizona blazes were the first major wildfires in the Grand Canyon state this year after a record 2011 fire season in which nearly 2,000 blazes consumed over 1,500 square miles (3,900 square km), according to the National Interagency Fire Center.
In northern Nevada near the California border, crews said two homes and 17 other buildings were charred and more than 100 were voluntarily evacuated on Wednesday as the Topaz Ranch Estates wildfire razed more than 9 square miles (23 square km) of brush and forest in Douglas County.
That voluntary evacuation was canceled later on Wednesday and residents were allowed to return home, authorities said, but the blaze is just 15 percent contained and poses a threat in foothills that are the driest they have been in 20 years.
"We're doing everything we can to keep it on the hill, but it could jump the line or come out the canyon," said Mark Regan, a battalion chief with the Lake Tahoe Fire Department.
"It's very steep terrain," Regan said, adding that fire engines cannot access the area, and firefighters have to hike on rough terrain to reach the blaze.
Nearly 600 firefighters fought the conflagration with bulldozers and helicopters, as billowing smoke cast a pall over the rugged area south of Carson City, making it difficult to assess the burn size.
"There's so much smoke, you can't really get up in the air and see ... the size," Rita Ayers, a spokeswoman with the Topaz Ranch Estates fire incident team told Reuters.
"Helicopters in front are trying to hold the fire moving too far to the east, and they have all the fighters around it putting in lines," she added.
The cause of the blaze is under investigation, Regan said.
COOLER TEMPERATURES EXPECTED
While gusting winds challenged firefighters, much cooler temperatures where expected to help crews bring the fire under control by Saturday.
Even as crews fought to contain the Nevada fire, more than 1,100 firefighters made slow progress against the most dangerous of the blazes burning in the U.S. Southwest, the so-called Gladiator Fire in Arizona.
That fire, which has torched more than 24 square miles (62 square km) of ponderosa pine and brush some 40 miles (64 km) north of Phoenix, was 26 percent contained on Wednesday, up from 19 percent a day earlier.
"The winds will start earlier today and will continue to get stronger as the day progresses," the fire incident team said. "Firefighters will continue to monitor for spot fires from flying embers outside of the fire lines.
The blaze, which threw a veil of grayish smoke over the northeast Phoenix valley, has forced the evacuation of about 350 residents of the old mining town of Crown King and three other tiny communities nearby.
Crews battling the largest of the four Arizona fires, the 25-square-mile (65-square-km) Sunflower Fire, had succeeded in reinforcing control lines and it was more than 40 percent under control.
A large human-caused wildfire that has scorched 18.5 square miles (48 square km) in Mexico crept across the border to Arizona, scorching 50 acres (20 hectares) of grass, brush and oak in the Coronado National Forest by late Wednesday.
In New Mexico, authorities said seven residents of the small summer community of Willow Creek were evacuated as a precaution because of a fire that charred more than 15 square miles (39 square km) in steep, rugged terrain of the Gila Wilderness area.