The Mill Flat fire is now 479 acres in size, according to the Dixie National Forest.
Lightning ignited the blaze July 25, and forest officials have allowed it to burn, as long as it remains in a predetermined area, for resource benefit.
The Forest Service policy for fire management in wilderness areas permits lightning fires to play out their natural ecological role, until it breaks the bounds of a predetermined area, when officials would take a more proactive role.
"It's not even close to getting to that point right now though, said Dixie National Forest spokeswoman Andi Falsetto. "The fire is being monitored daily."
Currently the fire is burning dead trees that can produce heavier smoke, officials said.
Smoke is visible from Cedar City, St. George and Enterprise, with heavy smoke seen in New Harmony.
The fire is paving the way for new aspen trees to flourish, creating openings in the conifers, officials said.
— Michael Gonda