A mother and her daughter were among six Russians killed after their snowmobile crashed through a safety barrier and fell 300ft in the Italian Alps.
Two others were seriously injured in the late night tragedy, which police have blamed on excessive speed and icy conditions on the Mount Cermis in north east Italy.
Officials said the run is usually lit at night but it had closed early because of the icy conditions, and was shrouded in darkness when the accident happened on Friday night.
The group were on black run known as Olimpia 2, and were returning to their two separate hotels after a night out.
Police said that some of the group were thrown from a trailer – not intended for passenger use - which was being towed by the snowmobile.
The snowmobile itself also had too many people on it.
A police spokesman added that the force of the impact threw the group from the trailer and snowmobile and into an area of rocks and thick forest.
A helicopter was called in to airlift the dead and injured from the mountain and one of those hurt was taken to the nearby hospital at Cavalese, while the other was flown to nearby Trento.
The dead - two women and four men - were named by police as Larissa Pshenichnaya, 51, the manager of the Sporting Hotel in Cermis and Liudmila Iudina, 48, who was killed along with her daughter Julia, 25, while her 17-year-old son Boris was seriously hurt.
The other victims were named as Irina Kravchenko, 45, Denis Kravchenko, Viacheslav Sleptsov, 52, while the other seriously injured man was are Azat Agafarov 47.
Those hurt do not have "life threatening injuries".
Police said that all of the group apart from Pshenichnaya and Agafarov were tourists from Krasnodar in southern Russia.
The group were in Italy to celebrate the Russian Orthodox Christmas on January 6 and the area is popular with Russian tourists who flock to the mountains every year.
Alcohol tests will be carried out on the two survivors.
Cermis mayor Silvano Welponer said: "I'm very sad that six people have lost their lives but at the same time this was an irresponsible act - they were on a closed black run at night, when they should not have been there. They chose to be there. It was not a mistake."
Witness Cesare Perini said: "We were coming down Olimpia 3, a run which was open and lit when all of a sudden a police snowmobile came racing up the slope with its lights flashing and siren on.
"When we got down to the bottom a policeman told us to get off the piste. The ski lift operator said the run was closing because there had been fatalities up the mountain."
In 1998, a US Marine jet, flying low on a training run from a nearby air base, accidentally sliced a ski gondola's cable on Mount Cermis, sending the cable car crashing to the ground and claiming 20 lives.