The Utah Avalanche Center says a snowboarder triggered the avalanche that killed a 27-year-old woman who was skiing at Snowbird.

According to a report posted on the UAC Web site, about 300 people crossed the starting zone and/or skied the slope that failed Dec. 14 on the High Traverse of Mount Baldy.

Investigators say the slide started when a male snowboarder was crossing the slope around 12:20 p.m. The snowboarder was not caught in the avalanche.

Witnesses say Heather Gross, a University of Utah graduate student, was climbing up the slope to retrieve a lost ski when she was buried by the avalanche. She died later at a hospital.

The U.S. Forest Service and Salt Lake County Sheriff's Office are continuing to investigate the avalanche.