A wildfire that destroyed two homes in a rural neighborhood near the California-Nevada line may have been caused by an illegal burn that had been smoldering at a private residence since the weekend, investigators said Wednesday.

Rugged terrain forced firefighting crews to concentrate on an aerial attack to try to slow the flames. The fire had consumed about 7,000 acres of mostly sagebrush, cheat grass, juniper and pinion as it burned in the mountains within miles of another residential area in rural Lyon County, about 60 miles southeast of Lake Tahoe.

No deaths or injuries have been reported, and evacuations have been lifted. There were no active flames near residential areas Wednesday evening, but officials said dozens of homes continued to be threatened because the fire was only 15 percent contained and hot spots remained within burned-out areas.

Northern winds blew smoke from the fire more than 350 miles southeast to Las Vegas, where a sooty haze obscured surrounding mountains and Clark County officials issued a smoke advisory.

Investigators believe the fire started when a resident failed to properly snuff out a burn Sunday and it suddenly burst into flames Tuesday afternoon at Topaz Ranch Estates.

Authorities initially indicated the burn likely was within the confines of a county permit that allows open burning of weeds and grass in rural areas when conditions are favorable.

But Douglas County Sheriff's Sgt. Jim Halsey said Wednesday a preliminary investigation indicates the residential burn exceeded the permit requirements, including ignition of materials prohibited under county regulations.

Halsey did not name the resident or provide other details about the burn, but he said the sheriff's office, Nevada state fire marshal and U.S. Bureau of Land Management were continuing to investigate.

One resident who lost everything said the fire department was called to a neighbor's home two days earlier when an intentional burn got out of control.

Fire officials would not comment, citing the ongoing investigation.

But Jack Taylor said the fire re-erupted Tuesday in the same place.

He was on the couch reading a book when he noticed the smoke. He grabbed a garden hose to try to protect the home where he lived with an elderly, disabled man he considered his grandfather, but the fire was swift and furious.

"After it hit the chicken coop, we ran," he said.

"I don't know what to do next," Taylor said, standing in front of the blackened hillside that used to be his home. He escaped with a few pairs of pants and some T-shirts. "I'm angry."

Authorities remain concerned because Thursday's weather forecast calls for relatively dry conditions and strong gusty winds, conditions that create extreme fire danger. As many as 560 firefighters were on-scene Wednesday evening.

Crews had dug a line around about 10 percent of the fire's perimeter, and full containment was expected by Saturday.

But the steep, rocky slopes in the foothills of the Pine Nut mountains were keeping most fire engines and heavy equipment away from active flames Wednesday as the fire burned to the east approaching the Upper Canyon Road neighborhood in the Smith Valley northwest of Wellington.

At least four air tankers and five helicopters were helping the mostly hand crews battling the blaze.

"It's difficult to get firefighting equipment up there so it is basically an air show at this point," Halsey said.

Authorities warned boaters to beware of helicopters dipping their aerial buckets in Topaz Lake to haul water to the fire.

Rita Ayers, fire information officer for the Sierra Front Interagency Dispatch Center, said two homes and 17 outbuildings had been destroyed by the fire. Authorities reported during the initial, frantic hours of the blaze that seven houses had burned, but they scaled that back Wednesday after determining several of those structures were not residences.

All evacuations had been lifted by Wednesday, but officials said approximately 120 residences, 300 outbuildings and numerous utility lines "continue to be threatened."

"Even though this area is doing pretty good, we could have some flare-up," said fire spokesman Mark Regan. "We have a lot of open line right not and a lot of hot spots."

Halsey said the fire had burned less than 10 acres when crews arrived at the scene at about 1:45 p.m. Tuesday, but the wind "just took off and (the fire) was growing like gangbusters."

"It shot across the valley real fast," said resident Diana Richardson, 69. Richardson said she and her husband were "just sitting here minding our own business" when they noticed flames halfway up a hill near their house in Topaz Ranch Estates. "It was scary."

Strong winds gusted steadily through Tuesday across a region that has seen very little moisture all winter, leaving vegetation dry and extremely flammable.

Betty Hathaway, 52, said the fire started behind her home in the foothills of the Pine Nut mountains and that a house two doors down "completely burned down."

"It was just a wall of fire," she said. "It is unbelievable my house did not burn down."


Associated Press writer Scott Sonner in Reno contributed to this report.