New details have emerged about the deadliest avalanche in California's history
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Among the findings, investigators claim the "best practice for backcountry travel" was not being followed, as the group size was large
Several skiers were also found to be wearing airbag backpacks, but none were deployed when the avalanche occurred on Feb. 17
Investigators are releasing new details about theavalanche that killed nine skiersin California's backcountry earlier this year.
On Tuesday, March 31, theNational Avalanche Center published its final reportabout the deadliest slide in the state's history based on findings by the Sierra Avalanche Center. There were 11 clients and four guides when the avalanche struck near Lake Tahoe on Feb. 17, killing nine people.
While the exact cause of the slide remains unknown, the findings don't rule out the possibility that the size of the group was a factor.
"Exposing only one person at a time to avalanche terrain is an accepted best practice for backcountry travel," the report states. "This group consisted of 15 people. Analysis of past avalanche accidents has indicated that larger group sizes (4 or more people) have a higher chance of being caught in avalanches."
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Two groups — six females with two guides, and another group of three males with two guides — had decided to combine for the return to the trailhead at the Castle Peak Snowpark on Donner Summit, according to the report.
The Blackbird Mountain guides led the group through an avalanche-prone area for unknown reasons, despite two alternative routes, per theSan Francisco Chronicle.
"This group traveled below avalanche terrain and through the runout zone of an avalanche path during a period when a natural or human-triggered avalanche was likely to very likely," the report states.
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At around 11 a.m. local time, the avalanche struck amid an "intense storm with very poor visibility," according to investigators. Continuous snowfall and strong winds, ranging from 60 to 125 miles per hour, had created hazardous conditions.
Several of the skiers were wearing airbag backpacks that could've helped them to stay on the surface when inflated. However, none were deployed when the avalanche struck, according to the report.
The findings confirm that 13 people were buried in the snow.
Many of the details about how the group responded to the slide come from two survivors who shared their experience withThe New York Times. They were near the rear of the group and not involved in the decision-making process, according to the newly published report.
The pair had fallen behind the rest of the group due to an equipment issue. This kept them from being caught in the slide and they were then able to save the lives of others.
"Two of the four buried survivors required companion rescue to excavate the snow that covered their airways," the report states. "The rapid location and excavation of these two individuals was lifesaving. At the time of the avalanche, the guide and client not caught in the avalanche, were a ways behind the rest of the group due to the client experiencing an equipment problem with one of their ski binding toe pieces."
"This separation may have kept them from being caught in the avalanche along with the rest of their party," the report continues, adding, "If other survivors who were closer to the front of the group and part of the group of women eventually choose to share their story, it may include different information and details."
PEOPLE has reached out to the Nevada County Sheriff's Office amid their criminal investigation into the avalanche. The Blackbird Mountain guides did not immediately respond to a request for further comment.
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