PORTAGE -- There were 220 firefighters near here and the Idaho town of Samaria on Monday working on the biggest wildfire in Utah this year.
According to Jason Curry, spokesman for the Utah Division of Forestry, Fire and State Lands, the fire was believed to have started Thursday evening and parts of the blaze were burning less than a mile from Samaria.
A hotshot crew constructed a fire line on Samaria's southern edge, so the threat to homes was minimal, fire spokeswoman Jennifer Hansen said.
The blaze, called the State Fire, was among several lightning-caused blazes burning Monday in Utah.
As of Monday morning, the fire in northern Box
Elder County had charred more than 25 square miles, reports said. But the fire grew by another 5 square miles during the day, Hansen said.
On Monday night, more than 21,000 acres had burned.
The blaze was 42 percent contained by Monday afternoon, but Hansen was unsure of the extent of containment Monday night.
"We were looking pretty good for the majority of the fire, especially in the areas of greatest concern, where there were structures threatened," Hansen said Monday night. "We did have an area in Gardener Canyon where the fire grew. Heavy fuels made it difficult to fight there."
Hansen said that, overall, firefighters were pulling back from fighting in areas of heavy fuels.
She said officials were using an indirect attack, constructing fire lines and letting the fire move into more desirable conditions for fighting.
"The heavier the fuels, the hotter the fire burns," she said. "The lighter fuels, the easier it is to suppress."
Two Utah National Guard Black Hawk helicopters were assisting the effort from the air, reports said.
Gov. Gary Herbert has authorized National Guard members to help fight the wildfires burning in the northern part of the state.
The governor's office said in a statement that extra air support from the Guard had been requested to help battle flames in steep canyons. Fires in other parts of the state have diverted scarce air resources, the statement said.
Hansen said a national incident command team was expected to take over management of the State Fire today.
She said that takeover would allow for more resources to be used to combat the blaze.
"Local resources have done what they can," she said.
Meanwhile, in Tooele County, the 4.5-square-mile Patch Springs Fire grew overnight Sunday as it approached the nearby Goshute Indian Reservation.
Firefighters were trying to secure the southern edge of the blaze, several miles from the town of Terra and homes on the reservation, fire information officer Joanna Wilson said.
Twelve homes, five commercial properties and five outbuildings, such as sheds and barns, were threatened, but no evacuations had been ordered.
Officials expected hot and dry conditions to continue, with wind gusts from the southwest.
Wilson said sandy roads in the area have made it difficult for crews to move their vehicles.
Roads and hiking trails were closed, and officials ordered three additional engines and another helicopter to assist the effort.
A third helicopter was deployed against the Millville Fire in Cache County, which has burned more than 3 square miles. About 150 firefighters were working to build a fire line around the blaze. No structures were threatened.
A red flag warning had been issued for the area, with the possibility of gusty winds and dry lightning until Monday night, U.S. Forest Service spokeswoman Charity Parks said.
Fire officials were also monitoring the 6-acre Mount Elmer Fire, which broke out Friday in the Mount Naomi Wilderness. Crews were not staffing the fire because resources were deployed against higher-priority
Also Monday, a firefighting crew from Delaware headed to Utah to help battle wildfires. A team of 20 wildland firefighters, trained under the Delaware Forest Service, was assigned to bolster the Utah ranks as blazes are fought on multiple fronts.
Standard-Examiner staff and wire reports contributed to this article.