U.S. 6 remained closed through Spanish Fork Canyon on Monday, after the Coal Hollow Fire jumped the highway and forced the evacuation of Diamond Fork Canyon.

According to officials, the fire — which was sparked by lightning on Aug. 4 — is becoming established in the Uinta-Wasatch-Cache National Forest. As of Monday night, it was 4 percent contained and is estimated to have burned 20,350 acres.

U.S. 6 was closed Sunday. It remains off limits to traffic from Diamond Fork to Tucker — mile markers 187-203.

The Utah Department of Transportation advised eastbound motorists to use southbound I-15 to U.S. 50 in Scipio to eastbound Interstate 70 as an alternate route, and westbound drivers to use westbound I-70 to U.S. 50 in Salina to northbound I-15. The detour adds about an hour to travel time.

The Diamond Fork Canyon evacuation was expected to remain in effect until at least sometime “later Monday,” fire officials reported.

The Coal Hollow blaze and five other fires in Utah continue to hamper air quality. According to the Utah Division of Air Quality, the levels in Utah County remained “red” (unhealthy for all people) for most of Monday, and “orange” (unhealthy for sensitive groups) in Salt Lake, Davis and Weber counties. On Monday night, those counties' air quality improved to “yellow,” or moderate.