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Aerial view of a wildfire spreading through a mountainous region, with smoke covering parts of the landscape and a road visible below.
This image provided by the USDA Forest Service shows the Alexander Mountain Fire near Loveland, Colo., Tuesday, July 30, 2024. (Jason Sieg/USDA Forest Service via AP)

Investigators have determined that the Alexander Mountain fire, which has burned nearly 10,000 acres in northern Colorado and destroyed 51 structures, was human-caused. 

The fire was sparked July 29 west of Loveland in Larimer County. As of Friday, it had burned 9,669 acres and was 91% contained.

The fire destroyed 26 homes and damaged at least four others, according to a report by the Larimer County Assessor. Twenty-one outbuildings were also destroyed.

U.S. Forest Service wildland investigators are working with the Larimer County Sheriff’s Office to chase clues on who may have started the fire, even if it wasn’t intentionally. 

Investigators are asking anyone with information about the start of the fire to call the Forest Service’s tip line at 303-275-5266. Photos, videos and typed statements can also be uploaded online

They are interested in information about anyone who was in the area immediately east and below the peak of Alexander Mountain, photos of the fire between 10:30 a.m. and 11:15 a.m. July 29 and information from anyone who spends time in the Alexander Mountain area.

All that remained in the backyard of 1657 Stone Canyon Drive were pieces of metal. The house, known as Pigeon Hollow, was one of five structures destroyed by the Stone Canyon fire near Lyons. (Tri Duong, Special to The Colorado Sun)

Alexander Mountain was one of three Front Range wildfires that officials have determined were human-caused and ignited the last week of July, before rain brought much-needed relief to extremely dry conditions. 

Arson investigators are still looking into the cause of the Quarry fire, which grew to nearly 580 acres in a highly-populated area of Jefferson County before firefighters got the perimeter fully under control earlier this week. 

On Saturday, officials from the Larimer County Sheriff’s Office and the Forest Service made their way to where they believed the fire started. Sheriff John Feyen said it was a “hard hike to get in there,” and that’s when they started their forensic investigation. They know the origin of the fire and that it was human-caused, but have not released further information on the investigation. 

Federal investigators are also looking into the Stone Canyon fire that destroyed five structures and is linked to one death in Boulder County. 

The cause of the fire is still unknown, but the involvement of the Alcohol, Tobacco, Firearms and Explosives, alongside Boulder County officials, indicates that authorities suspect it was human-caused.

Type of Story: News

Based on facts, either observed and verified directly by the reporter, or reported and verified from knowledgeable sources.

Olivia Prentzel covers breaking news and a wide range of other important issues impacting Coloradans for The Colorado Sun, where she has been a staff writer since 2021. At The Sun, she has covered wildfires, criminal justice, the environment,...