The 420-acre Treasure fire near Leadville was 80 percent contained Saturday and crews were working on the remaining hot zones.
"The crews have been working on mopping up the lines they burned," U.S. Forest Service spokeswoman Sarah Gallup said. "We're now feeling a little more confident. They're continuing to work on the last part of it that's got the most recent heat."
The blaze broke out June 21 approximately 10 miles southwest of Quandary Peak. It was only 25 percent contained as of Thursday, with lightning from recent thunderstorms setting crews back.
Officials say they're cutting back on personnel now that the fire is coming under control. A 10-person Americorps crew has been released and another team is expected to be sent home this weekend, leaving 40 firefighters and support staff next week.
Crews continue to systematically search for new spot fires outside the fireline, but haven't found any, according to reports. Only a few wisps of smoke and no flames are now visible from the interior of the fire.
Officials state they will continue to monitor the fire even after heat is no longer apparent to prevent rekindling.
The blaze did not threaten any structures, and no evacuation orders were issued.
The fire is believed to be human-triggered, and is still under investigation, according to official reports.
The fire broke out in the late morning June 21, when fire danger in the area was rated to be extreme and much of western Colorado was under a red flag warning. It exploded from four acres to over 300 the first day, but all subsequent growth was due to a firefighting strategy using controlled burn outs to wipe out the fire's fuel sources.
Though small, the Treasure fire proved difficult to fight. The blaze was situated entirely above 10,000 feet and in some areas reached as high as 12,000 feet, making the battle strenuous for firefighters, many of whom are from sea level and carrying heavy gear.
The accumulation of pine needles and debris under spruce trees in the fire's path also made the work of digging out fire lines time consuming.
The Treasure fire is burning 5 miles northeast of Leadville in Birdseye Gulch on the western side of Mosquito Peak.