After three days, the blaze has scorched an estimated 4,500 acres (1,821 hectares), and fire crews managed to carve containment lines around just 5 percent of its perimeter. The cause was still under investigation.
A recreation area belonging to the Air Force Academy was ordered evacuated due to its proximity to the fire, and all trails leading west of the school were closed, the base said.
Despite the fresh evacuations, the town of Manitou Springs, which had been evacuated over the weekend, appeared to remain out of imminent danger after residents were allowed back on Sunday.
Pam Staley, 60, a Colorado Springs resident, said she was concerned about the health effects of thick smoke and soot on many of her elderly neighbors who live in older homes without air conditioning.
"They sleep with open windows, and when the wind shifts, in the middle of the night, they get sick," she said as she stood watching the blaze from a safe distance at a local high school. Their eyes are watering, they're coughing. I'm really, really worried about them."
The wildfire was one of about a dozen burning out of control around Colorado, including the much larger High Park Fire near Fort Collins, a university town north of Denver close to the Wyoming border.
"We're going to be continuing to have to deal with these fires for weeks to come," U.S. Forest Service Chief Tom Tidwell said. "We anticipate it's going to be a long fire season."
To the east of the Waldo Canyon blaze, a fast-moving prairie fire apparently sparked by a blowout on a passing vehicle torched 45,000 acres (18,210 hectares) of grassland and ripped through the town of Last Chance, population 25.