A wildfire burning on the Utah-Juab county line continued to grow Monday as another wildfire threatened structures in Tooele County.

The Lonesome Pine fire has torched 556 acres of sage, grass and pinyon juniper about 3 1/2 miles northwest of Eureka. The fire was sparked Sunday, and the cause remains under investigation.

The Richfield Interagency Fire Center said multiple air resources, bulldozers and ground crews are being mobilized in an effort to quickly extinguish the blaze. Several roads in the area have been closed due to the fire.

In Tooele County, a wildfire was threatening about 20 structures on a ranch about two miles east of Terra.

The Gate Narrow fire had burned 250 acres of juniper, timber, shrubs and grasses by 9:30 p.m., said LaCee Bartholomew of the Bureau of Land Management.

No homes were being threatened, but about 20 structures were in danger, she said.

"They haven't done any evacuations or anything like that," Bartholomew said. "But with the winds they're experiencing, it's pushing the fire in that direction."

Fire crews, including six engines and an airplane, had the fire 10 percent contained late Monday. Crews planned to continue protecting the structures and working toward containment through the night, Bartholomew said.

State Route 199 between Terra and Rush Valley is closed because of the fire.

The cause of the fire is still under investigation.