Two prospects from the U.S. Ski Team were killed in an avalanche Monday while skiing near their European training base in the Austrian Alps.

The U.S. ski team said Ronnie Berlack, 20, and Bryce Astle, 19, died in the incident near the Rettenbach glacier near Soelden, the venue for the annual season-opening World Cup races.

Berlack, from Franconia, New Hampshire, and Astle, from Sandy, Utah, were part of a group of six skiers who were descending from the 3,056-meter Gaislachkogel when they left the prepared slope and apparently set off the avalanche. The other four skied out of the slide and escaped unhurt.

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Avalanche: Ronnie Berlack, left, was from New Hampshire and has died aged 20. Bryce Astle, 19, was from Utah

Young: Berlack, 20, stopped skiing in early 2014 because of a knee injury, but returned to racing over the summer

Promising: Astle was the top-performing junior skier at the U.S. Alpine Championships in Squaw Valley last March

Officials in the Tyrolean region said an avalanche alert had been declared for the area after days of heavy snowfall and mild temperatures.

U.S. Ski and Snowboard Association President and CEO Tiger Shaw said: 'Ronnie and Bryce were both outstanding ski racers who were passionate about their sport — both on the race course and skiing the mountain.

'Our hearts go out to the Berlack and Astle families, as well as to their extended sport family. Both of them loved what they did and conveyed that to those around them.'

Berlack grew up racing in New Hampshire and had been a student-athlete at Vermont's Burke Mountain Academy.

He was named to the so-called development team for potential World Cup racers following two top-20 finishes at the 2013 U.S. national championships and a spring tryout camp.

According to a ski team profile he came 11th in downhill and 17th in the 'super G' slalom race.

Off-piste: The two athletes, along with four others, were skiing off of marked trails on the Rettenback glacier, shown above in early winter, when the avalanche struck

The deaths took place after an avalanche on the Rettenbach glacier (marked above) in the Tyrol area of Austria, near its borders with Italy and Switzerland

He injured his knee in January 2014, but competed through the summer and raced in Chile and Canada before heading to Europe.

He was off to a strong season last year before suffering a knee injury last January. He had come back, competing in South American Cup races in Chile this summer and in NorAm and FIS races last month in Canada.

Astle was invited to train with the development team this season after strong early season results, including two top-10 results last month in Canada.

In a championship race at Squaw Valley, California, he came 13th in the giant slalom and was the top-performing junior racer.

At the NorAm Cup in Canada last month he finished on the podium in all but two events, ski officials said.

Snow slide: The skiers had been taking an unmarked route down the Rettenbach glacier while it was covered in fresh, heavy snows (not seen in the picture above)

Ski base: The two athletes died on a glacier near Soelden, Austria, the U.S. team's long-time base (file photo)

The disaster has left the U.S. ski team 'in shock,' Alpine director Patrick Riml told said in Zagred, Croatia, where the American slalom team was preparing for a night race on Tuesday.

'We are all very close,' said Riml, an Austrian who was born and grew up in Soelden. 'We train a lot in Park City. We'll see how they handle the whole thing and how they react.'

Riml added 'it's a shock for everybody. Two great boys, great athletes, good skiers. They were fun to have around. We are all in shock, still. It's very tragic.'

Berlack and Astle were part of a group of 10 skiers on the development team who gained experience in the Europa Cup and were preparing to race on the top-level World Cup.

'They all have the potential (to be on the World Cup),' Riml said. 'These two boys were among the other eight boys who are our future. We believed in these guys, that's why we selected them.'