(CNN) -- Firefighters in Reno, Nevada, have contained 80% of a wildfire there and expect to have it nearly completely contained by day's end, officials said Saturday.
The blaze has made 32 homes uninhabitable and damaged five, but is no longer a major threat to other structures, said Reno Fire Chief Michael Hernandez.
Some 140 firefighters were at or around the scene, containing the fire and mopping up hot spots and cleaning, he said.
"It's been a long, difficult 24 hours," Hernandez said.
The cause of the fire remains unknown, but the fire chief said his department has ruled out that the blaze started at a homeless encampment or that teenagers seen in the area were responsible.
Investigators believe -- though have not confirmed -- that high winds caused electrical arcing on a power line, which sparked the fire, Hernandez said.
"My assessment is that the first responders did just an incredible job," Nevada Sen. Dean Heller said.
Reno Police Chief Michael Poehlman said that about 50 officers were on the streets Saturday monitoring affected neighborhoods.
Starting at noon, residents were allowed to re-enter the area for the first time to survey their homes.
The city of Reno, the rest of Washoe County and Nevada all declared states of emergency Friday.
Authorities reported a fatality on Friday, but later determined that the fire evacuee had died of an apparent heart attack at 74.
One firefighter was taken to a hospital with first- and second-degree burns.
The fire was reported shortly after midnight Thursday, spreading within an hour and becoming a three-alarm blaze, Hernandez said.
The blaze had ballooned to 2,000 acres within about 12 hours, destroying some structures and causing minimal damage to others, according to the fire chief. He estimated that firefighters had saved 4,000 to 4,500 homes by Friday.
CNN's Shawn Nottingham and Deanna Proeller contributed to this report.