RENO, Nev. (AP) - A firefighter suffered first and second-degree burns and an elderly man died of a heart attack while trying to flee a sudden wildfire that spread through the Nevada Sierra foothills and roared into Reno on Friday, blanketing upscale houses, horse pastures and mountain roads in smoke plumes, amber flames and flying embers.

Authorities said the worst was likely over, but warned a change in the furious northern winds could refuel the sprawling fire that sent thousands of families fleeing their homes in the middle of the night and blanketed the region's mountain roads in flames. At least 25 properties were damaged and destroyed.

Fire Chief Mike Hernandez said flames still endanger some areas, but firefighters had largely contained the blaze that sent nearly 10,000 people from their homes in the middle of the night.

"We are actually backtracking and going over areas that have burned and extinguishing hot spots," Hernandez said.

Roughly 100 Nevada National Guard members were assisting local law enforcement in checking homes and keeping people out of the evacuated area. Health officials urged residents to stay inside and reduce physical activity, warning that the dust and smoke were adding to pollution levels in the affected regions and downwind neighborhoods.

Sixteen people were hospitalized, many for smoke inhalation. A 74-year-old man died of a heart attack while trying to leave his home.

The cause of the blaze wasn't known, but a downed power line or homeless encampments in the area might be to blame, Hernandez said. He said the region is also a popular area for teenagers who might have started the fire to stay warm.

Growing snow flurries and dropping temperatures late Friday afternoon stroked hopes that the remaining showers of ember and ash would die down quickly.

At least 400 firefighters from as far as 260 miles away flocked to Reno early Friday as multiple fires roared from the Sierra Nevada foothills in northwestern Nevada and spread to the valley floor. Police went house-to-house, pounding on doors and urging residents to evacuate in the dark of the night.

"The whole mountain was on fire," said Dick Hecht, who said when he escaped from his home with his wife, it was so windy he could barely stand. "It was so smoky, you couldn't hardly see."

The couple tried to return to their home before morning, but they were turned back by high winds and erupting flames. As they made their way back down the mountain roads, flames burned less than 40 yards from their vehicle.

Gusts of up to 60 mph grounded firefighter helicopters and made it difficult for firefighters to approach Caughlin Ranch, the affluent subdivision bordering pine-forested hills where the fire likely began after 12:30 a.m.

The strong winds combined with area's dry terrain helped the fire spread from 400 acres to 2,000, or more than 3 square miles. Firefighters said their efforts spared 4,000 homes, but that the disaster would likely cost multi-millions of dollars. The gusts were comparable to the Santa Ana winds that often aggravate and spread wildfires in the hills surrounding Los Angeles, officials said.