The backcountry ski trip hit by avalanche was led by an outfit offering mountain adventures globally

The group of 15 backcountry skiers headed out on a three-day trek organized by Blackbird Mountain Guides into pristine wilderness near Frog Lake in California's Sierra Nevada as a powerful winter storm moved into the state. The skiers on Sunday made their way to remote huts situated at 7,600 feet (3,415 meters) in Tahoe National Forest, carrying their own food and supplies. At 6:49 a.m. that same morning, the Sierra Avalanche Center had issued an avalanche watch for the area, indicating that large slides were likely in the next 24 to 48 hours. Two days later, as the group was making its way back out to a trailhead and the center increased the watch to a warning, an avalanche hit near Castle Peak, trapping the skiers. Authorities said Wednesday that eight people were killed and one person remained missing. Six skiers were rescued after sheltering in place for hours as search crews battled blizzard conditions. Nevada County Sheriff Shannan Moon said investigators were looking into the decision to proceed with the trip on Sunday despite the forecast for a major storm. "We're still in conversation with them on the decision factors that they made," Moon said at a Wednesday news conference announcing the deaths. Before the disaster, the tour company said its guides were highly skilled in dealing with extreme conditions and that it offered avalanche education. It's not known if the guides would have known about the avalanche warning as they returned to the trailhead. "If you've booked the Frog Lake Huts in Truckee, trust our guides to elevate your trip to the next level," the business said on its website, advertising the trip. "We'll navigate in and out of the huts, manage the risks, and find the best terrain and snow quality for you and your group!" Blackbird Mountain Guides said in a statement Tuesday that it was coordinating with authorities. Three of the guides were among those killed, officials said. The company, with offices in California and Washington state, offers mountaineering and backcountry ski trips across the U.S. West Coast as well as in Europe and Japan. The tour outfit also offers safety courses like wilderness skills and first aid. The rugged terrain where the skiers died had been closed to the public for a century before the Truckee Donner Land Trust bought it and opened the huts, which are outfitted with basic accommodations such as sleeping pads, gas stoves and flush toilets. The tour, which cost $1,165.00 per person, was rated for intermediate-to-expert skiers with at least 20 days of backcountry experience who should be prepared to climb up to 2,500 vertical feet (760 meters) throughout the course of a day, according to the company's website. Guides carry first aid kits and "wag bags" for human waste disposal, but participants must bring their own ski equipment and avalanche gear, including a beacon, shovel and probe. "Generally our guides are able to find excellent backcountry snow conditions, but often we need to travel through difficult conditions to access the goods," the website description said. "This requires riders to be adept with their backcountry touring skills and have a solid foundation of touring before the trip." Rapidly accumulating snow piling on fragile snowpack layers, along with strong winds, contributed to the treacherous conditions this week. The town of Soda Springs, near where the avalanche took place, recorded at least 30 inches (76 centimeters) of snow during a 24-hour period, according to the Soda Springs Mountain Resort. Associated Press writer Julie Watson in San Diego contributed to this report.