Authorities charged a U.S. Forest Service employee Sunday, accusing her of setting the fire that scorched more than 100,000 acres in Colorado and forced thousands to evacuate by burning a letter from her estranged husband in the Pike National Forest.

Forestry technician Terry Barton, 38, admitted starting the fire while patrolling the forest to enforce a fire ban, said assistant U.S. Attorney Bill Leone.

"She attempted to suppress the fire but it grew," Leone said.

Barton was charged with setting fire to timber in the national forest, damaging federal property and making false statements to investigators, Leone said.

She was scheduled to make an initial court appearance in federal court Monday.

Barton said she started burning the letter from her estranged husband within a designated campfire ring, where fires normally would be allowed, then tried to put out the blaze.

She initially told authorities she discovered an illegal campfire and had tried to put it out by throwing dirt on it, but it was too late. An investigation led the Forest Service to doubt her story, Leone said.

If convicted, Barton could be sentenced to up to 10 years in prison and fines of up to $250,000. She was arrested Sunday morning; it was not immediately clear whether she had an attorney.

"I want to begin by saying, this is one of the hardest announcements I've had to make in my career," said Rick Cables, regional forester for the Rocky Mountain Region for the U.S. Forest Service.

"I'm shocked and with a lot of other people, in a state of disbelief," Cables said. "I'm saddened to say that one of our employees has admitted to starting the Hayman fire."

Jody Penny, 45, out of her Florissant Heights home since Tuesday because of the fire, said she was sickened to learn the person suspected of starting it is from the area.

"We all wanted to believe it was some fool from somewhere else. You can understand that," Penny said. "That it's one of ours makes it real sad."

Firefighters gained ground Sunday on the blaze, which has burned within 40 miles of Denver city limits since it was started June 8, threatening southwestern suburbs and destroying at least 22 homes.

With the blaze about 35 percent contained, about 5,400 people remained out of their homes. It was one of seven fires burning in the state Sunday.

"Hopefully, this fire is going to now stay essentially where it is at," said Bobby Kitchens, a fire information officer. "We don't expect to see any more significant acreage gains."

Sheriff's deputies escorted some residents to retrieve belongings and assess damage, but didn't allow them to stay. Frustrated residents waited at the command post, trying to learn when they'll be able to return for good.

"It started to get to be a long period because one of the big things is I don't like eating out. I miss cooking at home," said Bob James, 46, who has been out of his home north of Lake George since Tuesday.

Another blaze flared in southwest Colorado and forced the evacuation of more than 330 homes. The latest fire had burned more than 26,000 acres in the San Juan National Forest by Sunday morning.

In addition to the evacuations, residents of 450 homes were told to be ready to leave. One cabin was destroyed, and fire managers were trying to determine whether others had burned.

More than 900 firefighters battled the blaze, about 10 miles north of Durango.

In California, 200 residents and campers returned home after fleeing a fire that burned 3,500 acres and destroyed five homes Saturday about 30 miles northeast of Bakersfield. Crews expected to contain the blaze by Tuesday.

Higher humidity and slightly cooler temperatures also helped crews battling fires in northern New Mexico. The state's largest blaze, which has blackened 92,500 acres on the Philmont Scout Ranch, was 75 percent contained and full containment is expected Wednesday.

The Associated Press contributed to this report.