A group of seven backcountry skiers who triggered a fatal avalanche in the San Juans were warned of significant avalanche activity and checked the forecast before the accident, according to a report released by the Colorado Avalanche Information Center.

Help from more than 30 agencies was needed to rescue three bodies from the avalanche, which trapped the skiers under snow funneled into a steep gully. Teams were not able to recover all their bodies until three days after the accident, due to the ...