GIRDWOOD, Alaska (AP) — Three skiers who had flown by helicopter to a remote mountain range were swept away by an avalanche and likely killed under the weight of dozens of feet of snow, Alaska State Troopers said Wednesday.

If the deaths are confirmed, it would be the deadliest U.S. avalanche since three climbers were killed in a slide in Washington’s Cascade Range two years ago.

While Alaska troopers had been unable to assess the site, “based on the information provided by the operator, unfortunately, we do not believe that any of the three missing persons survived the avalanche,” Austin McDaniel, a spokesperson for the Alaska State Troopers, said in a text to The Associated Press.

The slide caught the heli-skiers late Tuesday afternoon in the Chugach Mountains near the skiing community of Girdwood, located about 40 miles (64 kilometers) south of Anchorage, said McDaniel. Heli-skiers use helicopters to reach mountains in remote backcountry areas where there are no ski lifts, and then they either ski or snowboard down.

Guides from the heli-skiing company attempted to locate the trapped skiers using avalanche beacons and identified a probable area where they were buried, McDaniel said. But the victims were unable to be immediately recovered because of how deep they were buried, McDaniel said.

The snow deposited by the avalanche was up to 100 feet (30 meters) deep, and the skiers were likely buried at depths greater than 30 feet (9 meters), according to Chugach Powder Guides, which was running the trip.

The victims, all men, were clients from out of state who had been skiing with a guide on a run that’s used regularly by the company, according to Chugach Powder Guides spokesperson Tracey Knutson.

As the slide began, Knutson said, witnesses saw the men deploy their avalanche air bags — inflatable vests that are meant to keep avalanche victims above or close to the surface. A fourth person in the group was not caught in the avalanche, she said.

“Three guides on scene immediately issued a rescue alert and initiated rescue response,” Knutson said in a statement. As more guides and helicopters arrived to help, they picked up signals from the victims’ emergency beacons but decided there were not enough resources on site to safely recover them Tuesday, Knutson said.

Weather conditions as of midday Wednesday had not allowed state Department of Public Safety aircraft to reach the site, McDaniel said. It was rainy, windy and foggy in Girdwood, with snow at higher elevations.

The avalanche site was 8 miles (13 kilometers) northeast of the airport in Girdwood, in an area along the Twentymile River, according to the Chugach National Forest Avalanche Information Center.

An ongoing avalanche concern for the region has been a weak layer of snow buried 2 feet (0.6 meters) or more beneath the surface, said Andrew Schauer, lead avalanche forecaster with the Chugach National Forest Avalanche Information Center.

The center’s forecast for the area including Girdwood listed “considerable” avalanche danger at higher elevations on Tuesday.

More snow and wind Wednesday was adding weight “and making avalanches a little bigger and more likely,” Schauer said. A foot (0.3 meters) or more of new snow with strong winds was expected at elevations above about 1,500 feet (457 meters), he said. Conditions were expected to remain dangerous even after the storm system passes.

Girdwood is the skiing capital of Alaska and home to the Alyeska Resort at the base of Mount Alyeska, where people downhill ski or snowboard amid stunning views of Turnagain Arm. At the top of the mountain is the Seven Glaciers Restaurant, named for its view.

Each winter, 25 to 30 people die in avalanches in the U.S., according to the National Avalanche Center. Alaska ranks second behind Colorado for the most avalanche deaths in the nation, with 172 deaths since 1950, according to the center.

In 2021, Czech billionaire Petr Kellner and four others died in a helicopter crash during a heli-skiing tour near Knik Glacier, in the Chugach Mountains just north of Anchorage. A year later, a heli-ski guide scouting an area for clients died when an avalanche carried his body nearly 1,500 feet (457 meters) down a mountain, Alaska State Troopers said at the time.

Prior to this week’s accident, 15 people had been killed across the U.S. by avalanches this winter. The most recent was last Friday in Washington state, where three snowmobilers were caught in a slide that buried and killed one person and injured a second.

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Associated Press writers Becky Bohrer in Juneau and Matthew Brown in Billings, Montana, contributed to this report.