DENVER (KDVR) — Two separate fires combined to form the most destructive wildfire in Colorado history, an investigation into 2021’s Marshall Fire found. The results were announced Thursday by the Boulder County Sheriff’s Office.

A fire caused by the reignition of an extinguished residential burn on property owned by the religious group Twelve Tribes combined with a second fire likely caused by a damaged Xcel power line, Sheriff Curtis Johnson said.

No criminal charges will be filed, Boulder County District Attorney Michael Dougherty announced. He said the evidence did not justify charges.

“This fire was terribly disruptive and traumatic to so many people. We make our decision on criminal charges based on evidence not based on emotion,” Dougherty said.

The Marshall Fire began on Dec. 30, 2021, destroying 1,084 residential structures in Boulder County and seven commercial structures. Two people were killed in the fire, 91-year-old Edna Nadine Turnbull and 69-year-old Robert Sharpe.

Losses from the fire are estimated at more than $2 billion, with the most significant damage in the City of Louisville, Town of Superior and nearby portions of unincorporated Boulder County.

Johnson, who was sworn in as a sheriff in January, became emotional during the news conference, saying he was among those who lost their homes.

Dec. 24, 2021: Residential burn

On Dec. 24, 2021, six days before the Marshall Fire, residents at 5325 Eldorado Springs Dr. started a fire to dispose of scraps and tree branches. The property is owned by the Twelve Tribes group, the sheriff said.

According to the sheriff, the fire department checked on the fire that day and believes this burn was conducted responsibly, as there was a large water source nearby and the fire had been covered. The district attorney noted that the weather was rainy and cool that day.

However, the investigation found that on Dec. 30 high winds uncovered the previously buried fire, and the embers were exposed to oxygen and moved to nearby dry vegetation.

The residents tried to put out the reignited fire, the sheriff said, but the winds were pushing the flames faster than they could keep up.

The district attorney said 40 people were living on that property at the time and that there is no evidence that they set a fire on Dec. 30. He said criminal charges are not warranted, and said there is no evidence to prove that the fire conducted on Dec. 24 was criminally reckless.

Xcel power line

One hour after the reignited embers spread on Dec. 30, a second fire started on the Marshall Mesa Trailhead, the sheriff said.

Investigators determined the most likely cause was hot particles discharged from an Xcel Energy powerline. The powerline showed significant evidence of electrical arcing.

While the electrical line is the probable cause of the second fire, the sheriff said a coal mine fire underground cannot be ruled out. It is also unlikely, but not ruled out, that the embers from the first fire started the second fire that was 2,000 feet away.

High winds can cause the wires to disconnect, the sheriff said, and the investigation showed no evidence of worn materials or bad construction materials. Investigators found that the poles and conductors in the area were in good condition.

Shortly after the news conference, Xcel Energy provided a statement disputing the power line’s role in the fire, saying it believes the analyses used by the sheriff’s office “are flawed and their conclusions are incorrect.” The company did support that the fire started due to the residential burn.

“We believe the second fire burned into an area already burned by the fire from the first ignition, and did not cause damage to any homes or businesses. We strongly disagree with any suggestion that Xcel Energy’s powerlines caused the second ignition, which according to the report started 80 to 110 feet away from Xcel Energy’s powerlines in an area with underground coal fire activity,” Xcel’s statement said.

The investigation took over a year Dougherty said, because they wanted to exhaust every possibility, noting that the investigation was complex because it was started by two fires.