Firefighters battling three wildfires along Colorado’s Front Range continued to make significant gains in containment Sunday as more mandatory evacuation orders were lifted across Larimer, Boulder and Jefferson counties.

The Alexander Mountain, Stone Canyon and Quarry fires have burned nearly 12,000 acres, forced thousands of people to evacuate, damaged or destroyed 51 structures and killed one person over the last week.

But fire officials on Sunday spoke optimistically about firefighting efforts and the days ahead.

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The Stone Canyon fire burning north of Lyons reached 100% containment Sunday night and Boulder County officials lifted all evacuation orders for people living near the 1,557-acre blaze.

The fire, which killed one person and destroyed five homes since it started burning Tuesday, is being investigated as arson.

Containment on the 472-acre Quarry fire burning near Deer Creek Canyon increased to 35% on Sunday, Jefferson County Sheriff’s Office spokesperson Mark Techmeyer said at an afternoon briefing.

The fire, which forced nearly 600 homes to evacuate after it started burning late Tuesday night, has not destroyed any structures.

Fire crews are focused on proactive burning along the fire’s western edge to increase containment, Techmeyer said. There will be planned power outages in the mandatory evacuation area Monday as part of that effort.

Scattered showers on Sunday did not make an impact on the fire but provided a much-needed morale boost for the 190 firefighters on the ground, Techmeyer said. Most of the personnel on the fire are volunteers, he said.

“We’re really happy (with) where we are,” Techmeyer said. “It was a whole different situation on Wednesday and Thursday. Everything has worked out in our favor, and we’re going to get this thing done.”

Techmeyer did not release any additional details about the arson investigation.

“There’s nothing I can share, but we’re working on it,” he said. “We want this person as bad as everyone.”

Jefferson County officials hope the remaining mandatory evacuations will be lifted in the next few days, Techmeyer said.

More than 500 firefighters battling the Alexander Mountain fire 10 miles west of Loveland gained 54% containment on the 9,668-acre fire as of Sunday afternoon, county and federal officials said in a briefing.

Damage assessment teams finished surveying burned areas this weekend and found 26 homes and 21 outbuildings destroyed, Larimer County Sheriff John Feyen said at the briefing. Four homes sustained minor damage in the fire.

It’s possible more structures were damaged or destroyed that county officials don’t know about yet, Feyen said.

The cause of the fire is still under investigation. Investigative teams this weekend found signs of human activity and multiple lightning strikes where the fire started, Feyen said.

Larimer County officials lifted more mandatory evacuation orders Sunday morning and will meet with people at evacuation centers to verify addresses and distribute credentials so residents can return to their neighborhoods this week.

U.S. 34 will likely remain closed for another week so utility crews can repair infrastructure, Feyen said.

More than 1,000 contacts are still on mandatory evacuation status, Feyen said. Households often have multiple contacts.

The Alexander Mountain fire is contained on the eastern and southern edges, and fire officials attributed the containment gains to good decisions by fire crews and an influx in resources.

“We asked for the resources, it took them a little while to get there but because of the threat, because of the values around this fire, we were able to get what we needed,” said Southwest Area 1 Incident Commander Carl Schwope.

“Right now we’re at a good place for resources and that’s why you see the progress that you see, a lot of good folks doing a lot of hard work,” he added.

Some resources will likely start being released to respond to more critical fires in the coming days, Schwope said.

Crews fighting wildfires on Colorado’s Western Slope also saw containment gains this weekend, with the 193-acre Currant Creek fire burning near Cedaredge and the Grand Mesa in Delta County fully contained on Saturday.

The Bucktail fire burning across 3,515 acres northeast of Nucla in Montrose County was 5% contained as of Sunday afternoon, according to fire officials.

No structures are threatened and no evacuations are in effect, though the fire has shown “very high spread potential and is exhibiting active to extreme fire behavior,” fire officials said in an update.