A wildfire sparked by lightning on Sunday night had consumed more than 2,300 acres northwest of Tremonton as of late Monday and was still growing with no estimate of when the blaze would be contained, but no structures were threatened and officials said they did not expect evacuations of area residents would be necessary.

The Radio Hill Fire, which cast a cloud of smoke over the Northern Bear River Valley on Monday, marked the first significant blaze of the summer in Box Elder County. As of Monday afternoon it was 20 percent contained, with 120 firefighters from multiple agencies on the scene.

Box Elder County Fire Marshal Corey Barton said the firefighters included local agencies, crews from Cache and Weber counties, U.S. Forest Service personnel and others.

“It’s a delegated fire, so we have resources from all over the state to help us,” Barton said.

He said the fire wasn’t threatening any structures on Monday, although the communications equipment atop Radio Hill was close by. Large aircraft were dropping retardant on the south side of the fire nearest to where homes were located, and the fire was burning to the north, away from town, later in the day.

Lightning on Sunday night sparked two other blazes in the area, one of which combined with the Radio Hill Fire. The other fire, which broke out in the Marble Hills area, was contained to a small footprint.

In addition to the boots on the ground, there were five aircraft fighting the fire on Monday, including two DC-10s dropping retardant, two helicopters dropping water supplied by tender trucks at the base of operations, and one heavy prop plane.

Barton said the fire was being fed by an abundance of dry grasses and shrubs that have grown taller and thicker than usual following an unusually wet spring. Wind was also a factor, as the blaze jumped a double firebreak created by a bulldozer on Monday morning.

He said on Monday afternoon it was too early to predict when the fire might be contained.

“There’s lots of heavy fuel, and that’s a problem,” Barton said.

Officials reminded people to keep drones away from the fire, as there are current air-space restrictions. They also noted that there should be visible smoke around the area for a few days as things continue to smolder, and asked that people stay clear of the area, if possible.