Local authorities asked for a voluntary evacuation in Sedalia, a town 20 miles south of Denver, but stopped short of ordering people to leave.
Mass evacuations remain a possibility, although the likelihood has decreased since Monday, when authorities had alerted thousands of Denver residents to be prepared to flee the massive blaze.
The wind direction drove the fire back late Monday, but officials are still concerned it could gain strength.
“This fire is totally dominated by Mother Nature, all wind-driven and because of the drought conditions it’s that much more unpredictable,” U.S. Forest Service spokeswoman Susan Haywood said.
Ash continues to fall over southern Denver, causing shortness of breath as well as throat and eye irritation among many residents. The city is covered in yellow smoke, and a thick haze obscures the sun.
The blaze is believed to have started Saturday when a campfire about 60 miles southwest of Denver grew out of control. The fire continued to grow about one mile every five hours, and by Tuesday was still only five percent contained.
Campfires are prohibited on most counties’ forestland because of Colorado’s severe drought. Authorities did not identify the person thought to have built the campfire.
Colorado Gov. Bill Owens, who has closed three state parks and issued a statewide ban on fires and fireworks, has said the fire is thought to be the largest in Colorado history.
There are at least eight wildfires currently burning in Colorado, including one covering 10,000 acres in western Colorado that burned 24 homes.