A fast-moving wildfire burned through a hay field, killing a boy's father and grandfather but the youngster managed to escape.
The 11-year-old boy's father, 43-year-old Tracy Houston, and grandfather, 63-year-old George Houston, were killed by the flames, authorities said. A third man, 75-year-old Roger Roberson, was flown to Salt Lake City and died overnight, officials said Saturday.
The boy was treated at and released from a hospital in Roosevelt, according to a newspaper report.
The fire started north of Neola, about 100 miles (160 kilometers) east of Salt Lake City, on Friday morning. By Saturday afternoon, about 23 square miles (60 square kilometers), including part of Ashley National Forest in the northeastern corner of the state, had been consumed.
"A fire wall came over that hill," Uintah County Sheriff Jeff Merrell told the Deseret Morning News. "The officers who were here said it just started sucking up all the air."
Trevor Quick, a friend of the family, said the men apparently told the boy to run.
Gov. Jon Huntsman requested aid from the Federal Emergency Management Agency after being flown over the area.
In California, evacuated residents were returning to their burned-out streets Saturday after a separate wildfire near Lake Tahoe destroyed more than 200 homes and charred 3,100 acres (1,255 hectares), displacing about 3,500 people. Investigators said the blaze was started by an illegal campfire and was 80 percent contained.
More firefighters departed the Lake Tahoe region. About 1,300 remained Saturday, compared with more than 2,000 the day before, said Steve Johnson, a spokesman for the U.S. Bureau of Land Management.
Both wildfires were fueled by dry conditions in the West. In Utah, wind gusts Saturday were expected to reach up to 25 mph (40 kph), fanning the flames even more. The cause of that wildfire was unknown.
Meanwhile, north of Los Angeles, fire crews had a 19-square-mile (49-square-kilometer) blaze 80 percent contained, state fire department spokesman Rick Espino said Saturday.
"We still have some areas of concern, but it's looking pretty good," Espino said.
Four crew members had been injured battling the blaze that destroyed 12 homes and six buildings since it broke out Sunday night in steep canyons south of the San Joaquin Valley, officials said.
And in Montana, a nearly 6-square-mile (15.5-square kilometer) blaze near Yellowstone National Park was 60 percent contained Saturday, officials said. Evacuation orders remained in effect for 45 to 50 summer homes.
Russian officials have repeatedly declared that Israeli aviation poses a threat to the Russian military in Syria.