Emergency services are searching Mont Maudit in the French Alps for survivors following an avalanche which has killed nine people.
A spokeswoman for the Préfecture de la Haute-Savoie said: "Nine people are dead, three of them British. It is not known whereabouts in the UK they are from."
Local media reported that the dead also included two Germans, two Swiss and two Spaniards.
It is understood 28 climbers from several countries were taking part in the expedition at the time.
Police said they were alerted at about 5.25am local time.
Several dozen gendarmes and other rescuers along with two helicopters worked to pull the dead and injured from the mountain.
The injured climbers were taken to hospital.
Christian Trommsdorff, vice president of the French Guides Association, told the BBC: "Unfortunately this morning there's been a big slab avalanche.
"We don't know exactly how it was triggered.
"It is at fairly high altitude there, so it is a snow avalanche.
"It was triggered by either the people who are climbing themselves or by some ice fall above, we don't know yet."
Mont Maudit is 4,465 metres high and part of the Mont Blanc range. It means Cursed Mountain in French.
The area is one of the most popular with climbers in the Alps.
Chamonix-based mountain guide Richard Mansfield said the route where the accident happened was the second most popular to the top of Mont Blanc.
Mr Mansfield said it was not unusual to have 100 people a day use it.
He said: "It's a very beautiful area and a common route but it can have very serious consequences, particularly due to avalanches."
Mr Mansfield, who runs mountainadventureguides.co.uk, said the slopes on Mont Maudit face away from the prevailing wind which means snow is pushed over, forming slabs.
"These can easily be set off by a passing climber, causing an avalanche."
He said the climbing group would be roped together as they used this route, usually just one and a half arm spans apart.