State investigators blamed a fatal December ski lift accident on two factors – a malfunction of a recently modified electrical drive and control system on the Quick Draw Express and repeated speed changes “immediately prior” to the moment a Texas woman was thrown to her death, according to the final report made public Thursday.

The result was an “unprecedented” occurrence that flung Chair No. 58 into a support tower which, in turn, hurled the woman and her two daughters onto the hard-packed snow below.

Kelly Huber, 40, of San Antonio, Texas, died Dec. 29 after a fall of approximately 25 feet, and her daughters, ages 9 and 12, were seriously injured in the incident.

A statement from one witness said the woman and her daughters did not have the safety bar down on their chair.

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Ski Granby Ranch released the following statement regarding the report:

Granby Ranch is reviewing the report released yesterday by the Colorado Passenger Safety Tramway Board on the incident at Granby Ranch on December 29, 2016. This is a 151 page report that deserves careful review. Granby Ranch continues to comply with all Tramway Board directives. We would again like to offer our condolences to the Huber family for their loss. Granby Ranch is committed to the health and safety of its guests.

The state could still take disciplinary action against the resort – but that decision is pending.

It was clear from the 151-page report by the Colorado Passenger Tramway Safety Board that the incident was highly unusual. In one footnote, the investigators wrote: “Due to the unprecedented nature of this dynamic occurrence, continued investigation/analysis of this event will likely continue for years.”

The report also said, “No one on the investigative team has ever witnessed or heard of a similar event. Likewise, literature does not describe such an event.”

The report called modifications to the electrical control system for the lift “the primary cause of the incident.”

Those modifications were made in early December. A state inspector examined the lift on Dec. 5 and again three days later. After requesting – and obtaining – additional documentation, the Passenger Tramway Safety Board licensed the lift for operation on Dec. 15.

But while the report faulted the electrical control system as the primary cause, it also suggested that it was exacerbated by multiple speed changes – something described by numerous witnesses.

One man sent an e-mail to state investigators two days after the incident, describing unusual operation of the lift when he’d been at Ski Granby Ranch the week before.

“We raised concerns about the lift operation as it was much different than in years past,” the man wrote. “I mentioned it to a Granby Ranch official and my wife also talked with one of the mechanics that was there to work on the lift.

“The intense, hi amplitude swinging and bounce was way out of the ordinary and appeared to be a change in operational procedure to speed skier transport.”

The report suggested that an unidentified operator altered the lift’s speed. That determination was based, in part, on statements from multiple witnesses and information collected by a device on the lift known as a “data logger.”

“According to the operator, he did not remember making any speed change prior to the incident,” the report said, in part.

The report noted that while the “data logger” does not record changes in speed, “there is supporting evidence indicating that rapid and significant accelerations/decelerations of the lift occurred immediately prior to the incident.”

Multiple witnesses described erratic behavior by the lift in the moments leading up to the incident.

“My chair started an up and down swing around tower 3,” one man wrote. “About half-way to tower 5 I heard a ‘thunk’ and felt a rattle through the line. I turned around to see 3 people falling and chairs behind with a horizontal swing.”

In a follow-up statement, he called the lift’s movement “the largest vertical motion I had ever felt in a lift line.”

“I would like it to be noted that the mother was visibly holding one of the children in what appeared to be an attempt to protect the child from the impact of landing.”

Another witness wrote, “We started swinging side to side. My son’s side almost hit (the) pole.”

After recounting seeing the woman and children after the fall, the man wrote, “Don’t let her die.”

The report noted that data captured by the lift showed that at the time of the accident the lift was accelerated into the “fast” position – the Quick Draw Express’s maximum licensed design speed – and that evidence indicated “that the operator had not allowed the QDE lift to reach its steady state speed before” moving its control into the “fast” position.

At the same time, the modifications to the electrical control drive, the investigation found, “may have resulted in the drive trying to respond too aggressively to lift demands when changing from ‘Fast’ to ‘Slow’ and back to ‘Fast’ again.”

Despite the electrical control issues, investigators could only re-create the situation during testing “by rapid changes in the lift speed with the newly installed drive.”

The operator of Ski Granby Ranch had suggested back in January that a contractor’s modifications to the electrical drive and control system of the Quick Draw Express led to the tragedy. That statement made no mention of the possibility that a lift operator’s actions contributed to the incident.

The report made public Thursday came months after Investigators had concluded “that environmental factors, weather, and the occupants of Chair No. 58 did not contribute to the cause of the incident.”

Huber suffered a traumatic rupture of her aorta, the main artery leading away from the heart, according to an autopsy. She also suffered other blunt force injuries.

Fatal lift accidents are rare: Since the Colorado Passenger Tramway Safety Board was established in 1965, there have been three deadly lift incidents in the state that have claimed a total of seven lives – a 1976 incident at Vail that killed four people, a 1985 incident at Keystone that killed two people, and the incident at Ski Granby Ranch.

Contact 9NEWS reporter Kevin Vaughan with tips about this or any story: or 303-871-1862.