Interagency Fire Center spokesman Jason Curry characterized the potential for further spread of the Lost Lake blaze as "extreme." That assessment also applied to the physical challenges more than 320 firefighters aided by water-bearing helicopters faced in battling flames that were periodically jumping from the crown of one tree to another with gusts of wind.
Curry said Thursday at about 6:30 p.m. that the fire had been 10 percent contained.
The cause or causes of the Lost Lake Fire which began as a series of smaller blazes that merged on Wednesday remained under investigation, but it was believed to have been human-caused.
The largest, still active blaze was the White Rock Fire in the Hamlin Valley area along the Nevada-Utah border, about 25 miles northeast of Caliente, Nev. GPS mapping showed it had blackened 6,355 acres as of mid-day Thursday.
Sparked by lightning on June 1, the fire was 90 percent contained Thursday night. Officials hope for full containment by Saturday.
Meanwhile, a voluntary evacuation order issued for about 20 summer cabins in the Monroe Meadows area remained in effect near the 2,300-acre Box Creek Fire. U.S. Forest Service spokesman John Zapell said the acreage was revised from 700 acres to include acreage that had burned from the earlier prescribed fire management operation that went out of control Monday.
More than 220 firefighters battled the Box Creek Fire, which continued to blacken mixed conifer and aspen forests five miles northeast of Greenwich, near Fishlake National Forest. They estimated the blaze was 15 percent contained Thursday.
The Lake Creek Fire in Garfield County, about 10 miles northwest of Boulder and 15 miles north of Escalante, had topped 1,100 acres. About 120 firefighters were battling that blaze, but no estimate for its containment had been made.
Tribune reporter Jessica Miller contributed to this story.