A fast-moving wildfire in southeastern Utah County grew to more than 6,600 acres by Wednesday night, tripling in size from the morning's estimate and prompting the handful of residents in the largely remote and rural area to evacuate.

“It's making some rather extreme pushes right now,” said fire information officer Leann Fox.

The Coal Hollow Fire, which lightning sparked Saturday, has quickly eaten through thick juniper trees and dry brush. Crews had no containment as the blaze inched closer to homes four days later, threatening at least five structures.

Utah County sheriff’s Sgt. Spencer Cannon said evacuations were ordered west of Scofield Reservoir and in the Soldier Summit area along U.S. Highway 6. There are maybe a dozen cabins in that area, he said.

“Search and Rescue is assisting with notifying campers and the few residents in these areas,” Cannon tweeted late Wednesday.

The fire sent up a mushroom cloud of smoke that was visible from more than 30 miles away in Provo and Alpine. The smoke settled in the valley, too, making it hard to see by nightfall. Officials cautioned drivers to use their headlights.

A hundred firefighters battled the blaze that ballooned in the Manti-La Sal National Forest with heavy winds. It was at 1,100 acres Monday.

“The area is extremely dry,” Fox said. “It's perfect fire conditions.”

Meanwhile, the neighboring Hilltop Fire in central Utah’s Sanpete County, which began Monday afternoon, saw minimal growth Wednesday. It had burned about 1,800 acres southeast of Indianola and was 12 percent contained.

About 40 percent of residents were evacuated from the town and nearby estates after the blaze claimed at least two structures; firefighters were trying to save nearly 200 more still standing in its path.

Earlier Wednesday, the major candidates in Utah’s U.S. Senate race disagreed about what is to blame for the recent rash of wildfires. Jenny Wilson, a Democratic Salt Lake City Councilwoman, cited climate change while Mitt Romney, the Republican candidate and former presidential nominee, cited what he called government failure.