6-year-old girl never strapped into seat before fatal amusement park ride: Report

The 6-year-old girl who died on a ride at a Colorado amusement park earlier this month was never strapped into her seat -- and two operators failed to notice even after a monitor alerted them to a seatbelt safety issue -- before the ride plunged 110 feet, according to a state investigation.

Wongel Estifanos was visiting Glenwood Caverns Adventure Park, located atop Iron Mountain in Glenwood Springs, with her family on Sept. 5 when she went on the Haunted Mine Drop ride, a free-fall drop down a pitch-black shaft.

After reviewing video surveillance and operating manuals, investigators with the Colorado Division of Oil and Public Safety determined that when Wongel got on the ride, she sat in a previously unoccupied seat on top of two already-locked seatbelts, and that "multiple operator errors" and "inadequate training" contributed to the fatal accident, according to a report released Friday.

The girl was only holding the tail of one seatbelt across her lap, but when checking her seat, a ride operator "did not notice that the seatbelts were not positioned across her lap," according to the report.

The ride's control panel alerted the operator to an error with one of the seatbelts on Wongel's seat, indicating that that seatbelt had not been properly unlocked after the previous ride cycle, according to the report. The operator returned "multiple times" to check the seatbelt and buckle it to no avail, but "did not believe the error because they were convinced the restraint had been cycled," the report stated.

A second ride operator then unlocked the seatbelts using a manual switch, clearing the error on the ride's control system, "without unloading passengers to determine what the issue was," the report stated. This decision did not resolve the problem -- that Wongel was not wearing the seatbelts -- and demonstrated that the operator "did not have a complete understanding" of the control system's safety indicators, according to the report.

The second operator also checked the girl's seatbelts but "did not notice that neither of the seatbelts were positioned across her lap," according to the report.

With no error on the control panel, the second operator was then able to dispatch the ride.

"Because Ms. Estifanos was not restrained in the seat she became separated from her seat and fell to the bottom of the [Haunted Mine Drop] shaft, resulting in her death," the report stated.

Operators were not formally trained to unbuckle all seatbelts following each ride, though it was common practice and one that the first operator performed "inconsistently" on earlier rides, according to the report.

The operators are supposed to buckle the seatbelts for each of the ride's six passengers and confirm the restraints are over their laps, per the manufacturer's operating manual, as "passengers cannot be expected to know or correctly execute the safety procedures for this ride," the report stated. Both operators failed to follow these procedures, according to the report.

The report also determined that the operators' training "did not appear to emphasize the inherent risks of the ride," and that the manufacturer's operating manual "does not instruct operators on how to properly address errors."

The Haunted Mine Drop is currently closed, and future plans for the ride are "undetermined," the amusement park said.

"Safety is, and always has been, our top priority," Glenwood Caverns Adventure Park founder Steve Beckley said in a statement following the release of the report. "Since opening our first ride just over 15 years ago, Glenwood Caverns Adventure Park has delivered more than 10 million safe and enjoyable rides."

"We have been working closely with the Colorado Division of Oil and Public Safety and independent safety experts to review this incident," he continued, noting that the amusement park will review the report "carefully for recommendations."

"More than anything, we want the Estifanos family to know how deeply sorry we are for their loss and how committed we are to making sure it never happens again," he added.

In a statement to Denver ABC affiliate KMGH, Dan Caplis, an attorney for the Estifanos family, said that Wongel's parents had received the report and called on people who have "experienced problems" with the Haunted Mine Drop to come forward.

"Wongel's parents are determined to do everything in their power to make sure that no one ever dies this way again," said Caplis, who told the station he intends to file a lawsuit against the park on behalf of the family.

ABC News' Will McDuffie contributed to this report.