The BBC's Angus Roxburgh: "It is Frances' worst ever cable car accident"

President Jacques Chirac said the entire country was in mourning.

Relatives gathered in the local church around midnight for a religious service.

Coffins containing the dead were brought to the church from the cable car station where they had been taken for identification following the early morning accident.

Earlier,the mayor of the ski resort, Mayor Jean-Marie Bernard, weeping and in shock, said: "The cable car fell. We don't know why ... These are working people and they are dead."

He said they had a duty to the victims' families to determine the cause of the accident.

"The mountains are in mourning today ... nothing could have led us to expect such a disaster," he said.

There are conflicting reports as to how the cable car fell. The local authorities initially said that the cable itself had snapped. But it was later suggested that the cabin had somehow become detached from the cables.

Medical assistant Magali Espinasse, who visited the scene of the accident, said the bodies were scattered all over, "like in a plane crash".

No survivors were found at the scene and all 20 bodies were recovered from the wreckage and taken to the local church.

Observatory workers

The cable car was privately owned by a Franco-German scientific enterprise and used to transport staff and equipment to an observatory high in the mountains.

The BBC's Stephen Jessel: No-one knows how the car became detached from the cable

It was not used by tourists or the public at large.

Passengers included building workers, cleaning staff, scientists and telecommunications engineers.

Nearly everyone in the resort, which has a population of just over 500, is said to know at least one of the employees of the observatory who were heading to work on the mountain top when the cable car plunged to the ground early on Thursday.

Local tourist official Yvan Chaix said: "We know most of the victims. The whole region is in shock."

"The accident is a surprise for all of us because the cable car was used daily by people at the observatory," he said.

Government sympathy

French cabinet ministers who visited the crash site said it was too early to speculate on the cause of the tragedy and expressed the deep sympathy of the French Government to the relatives of those who died.

Rescue teams rushed to the scene

French Interior Minister Jean-Pierre Chevenement and Labour Minister Martine Aubry visited the scene of the crash, before arriving in the village itself to meet victims' families.

At a news conference they said the whole government wanted to express its condolences to the victims' families.

"Jean-Pierre Chevenement and myself have said to the families that, although obviously it won't do much to ease the pain and distress they are feeling now, the investigation from the start will be completely open and very thorough, " the French labour minister said.

Mr Chevenement said the French president and the whole government were very saddened by the horrible tragedy and were visiting "to express our feelings of deep pain and compassion to the families who are facing this situation with great courage".

The number of dead is the highest toll since 1976 when 42 people died at Cavalese in the Italian Dolomites, the world's worst cable car accident.