Authorities and survivors of a deadly avalanche on France's Mont Blanc say the disaster was nearly impossible to foresee.

Climbers continued to set off up slopes in thick clouds Friday, the day after the avalanche swept nine to their deaths.

Britain's ambassador to France, Sir Peter Ricketts, says those who died "were doing nothing imprudent," and there were "no indications of an avalanche" ahead of time.

Survivor Daniel Rossetto, a guide quoted in France's Le Parisien newspaper, described being tossed and trapped by the snow and trussed up "like a sausage" in his rope.

Three Britons, three Germans, two Spaniards and a Swiss climber were killed.

Authorities say the avalanche could have been caused by a sheet of ice breaking off, or by a climber inadvertently setting a slab loose.