Jefferson County sheriff’s investigators determined the Quarry fire near Deer Creek Canyon was started by humans, launching an arson investigation into a second Colorado wildfire this week.

The causes of three Front Range fires remain under investigation with local sheriffs asking for public tips and receiving investigative help from state and federal agencies.

Meanwhile, firefighters started gaining control of those fires on Friday while a fourth broke open in southwestern Colorado and charred more than 2,000 acres.

So far, the four fires have burned more than 11,000 acres and are stretching resources across the state as hot weather exacerbates burn conditions. As of Friday night, the fires have killed one person, damaged or destroyed at least 30 buildings and led Gov. Jared Polis to deploy the Colorado National Guard.

Thousands of people have been evacuated from homes although officials in Boulder County started reopening some areas that had been threatened by the Stone Canyon fire near Lyons. In Jefferson County officials were advising residents to visit an evacuation center to apply for passes to reenter neighborhoods although they did not know exactly when residents would be allowed back in.

Dry weather and temperatures in the high 90s during the week along with dry grass and brush have sped the fires’ expansion. Warmer weather caused by climate change make conditions in Colorado more conducive to fires, data show.

Two fires, the Quarry and Stone Canyon fires, are believed to have been human-caused and authorities have opened arson investigations.

Jefferson County sheriff’s investigator Kevin Bost said the Quarry fire near Dear Creek Canyon likely was caused by people. However, he did not specify whether investigators believe it was intentional or accidental. He also did not say what evidence investigators found.

Sheriff’s spokeswoman Karlyn Tilley on Friday afternoon asked for people who might have helpful footage on their home security cameras or others with tips to call a hotline at 303-271-5612. The sheriff’s office also is being helped by Colorado Division of Fire Prevention and Control dog that can detect fire accelerants.

The Quarry fire grew 50 acres on Friday, burning a total of 480 acres since it started Tuesday night in Deer Creek Canyon Park above Grizzly Drive where the trail has multiple switchbacks. But Tilley said fire crews made progress Friday when they were able to connect a fire line on the east and south sides after bulldozers plowed one side and firefighters on the ground dug a trench in steep, rocky terrain.

Stone Canyon fire investigators are receiving help from the U.S. Bureau of Alcohol, Tobacco and Firearms to determine the cause of that fire, which has burned 1,553 acres near Lyons.

Nathan Hallam, the Stone Canyon fire incident commander, said in a briefing on Friday afternoon that crews had contained 53% of the fire and hoped it would be fully contained by Sunday.

In Larimer County where the Alexander Mountain fire has destroyed more than 9,100 acres fire crews were trying to keep the fire from spreading west and jumping U.S. 34 near Drake, Jayson Coil, the operations section chief, said in a Friday afternoon update.

“That is the area where we are focusing all of our efforts,” he said.

Crews are worried that the fire could jump the highway, essentially shutting off access to the fire zone, Coil said. They also do not want flames to start hot spots on Sheep Mountain, and they want to protect homes in the Cedar Park subdivision.

On the east side of the Alexander Mountain fire crews are trying to prevent it from spreading into the burn scar left by the 2020 Cameron Peak fire, Coil said.

Private insurance companies have sent fire engines to protect individual homes that they cover, Coil said. Those engines will not be involved in general firefighting and will only use water on homes that are insured by certain companies and are threatened by flames.

Finally, the Bucktail fire spread across 2,046 acres of wildland on Friday after sparking on Thursday afternoon. It is burning in woodlands near Nucla and the Uncompahgre National Forest. No evacuations had been ordered as of Friday evening, according to the Inciweb website that monitors wildfires.

All of the fires led Colorado Department of Public Health and Environment officials to issue air pollution alerts across the Front Range and in Montrose County. Smoke, soot and ash from wildfires can enter people’s lungs during outdoor activities and cause breathing difficulties, especially in the elderly, young children and those with heart and lung diseases such as asthma.

Originally Published: August 2, 2024 at 7:47 p.m.