Two prospects from the US ski team have been killed in an avalanche while skiing near their European training base in the Austrian Alps.

Ronnie Berlack

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

Berlack and Astle were part of a group of six skiers who were descending from the 3,056-metre Gaislachkogel when they left the prepared slope and apparently set off the avalanche. The other four escaped unhurt.

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

US Alpine director Patrick Riml said the team "is in shock".

US Ski and Snowboard Association president 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.

Bryce Astle

"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 development team for potential World Cup racers following two top 20 finishes at the 2013 US national championships and a spring try-out camp.

Astle, from Utah, was invited to train with the development team this season after strong early season results, including two top 10 results at NorAm Cup races last month in Canada.

"We are all very close," said Mr 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."

He 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)," Mr 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."

Soelden has been the European base for the US ski team since 2011.