"Because of the size of the fire and the complex logistics of dealing with such a large area of impact, travel, and communications, the fire will be divided operationally", according to a release by the Utah Division of the Forestry Fire State Lands.
Officials say the fire now covers almost 67 square miles (174 square kilometers) and is 10 percent contained.
The Utah firefighters could face more challenges on Monday because the National Weather Service warned of critical fire weather conditions with gusty winds, high temperatures and low humidity.
The Utah blaze was accidentally started June 17 by someone using a torch to burn weeds.
In California, a vehicle accident started a fire in Santa Clarita in Los Angeles County, triggering mandatory evacuations in some neighbourhoods, the Los Angeles Times reported. No injuries were reported and more than a dozen residential buildings were damaged.
About 1,000 personnel are fighting the fire. Some residents are being allowed to return to their homes with escorts.
Firefighters also responded to other smaller fires across the region.
Photo Firefighters battled a fast-moving fire in Santa Clarita, Calif., on Sunday. Cal Fire officials said the cause of the brush fire was a single-car crash. One woman said, "I just hope I can go back to rotten food in the freezer and the refrigerator stinks like all get out". The freeway has reopened and the fire is 57 percent under control, he said on Monday afternoon.
Officials say the fire is 10 percent contained. The wildfire has already forced an evacuation of over 1,500 people, according to local broadcaster KUTV.