Another six are injured and at least three people are still missing, feared dead.

Earlier reports that another body had been found in the water turned out to be false.

A local police spokesman said the victims came from Australia, New Zealand, the UK, Canada, the United States, South Africa and Switzerland.

John Mcintyre : "High risk adventure turned to grief"

The police said the victims were among a party of 45 tourists canyoning with eight guides in the Saxeten Bach Gorge near the resort of Interlaken.

The police said it would take "days or weeks" until all the victims were identified.

Most of the fatalities suffered injuries to the head and the canyonists were all wearing identical protective gear - so dental records will have to be used for identification.

Dangerous sport

Canyoning is an adventure sport which involves climbing down gorges, and body surfing down mountain rapids and waterfalls without a raft.

The accident was discovered at around 1800 local time on Tuesday (1600 GMT) by a jogger who saw bodies floating into Lake Brienz, near Interlaken.

The victims had apparently been swept down from a nearby canyon, possibly in flash floods following a sudden thunderstorm.

"I saw huge pieces of wood in the water," said Andreas Haesler. "Then I saw bodies - one on its stomach, one on its back. They were all wearing life jackets but it was clear they were dead."

Helicopters and teams of rescuers are on site and an investigating judge has been called to the scene.

Ann Hall tells how her son's friends died in the disaster

The mother of one of the six injured people told how her son had tumbled down about six waterfalls after being hit by what he described as "a massive wall of water".

New Zealander John Hall, who is in hospital with back injuries, told his mother Ann that a lot of his friends had been killed, but that staff were shielding him from the extent of the tragedy.

Thunder and lightning

The expedition had been organised by Adventure World, a Swiss company based in nearby Wilderswil, which is popular with Americans and Japanese.

"It's awful," said Georg Hoedle, one of the company's managers, as he choked back tears at a news conference.

"We've been organising canyoning for six years and until now have only had the occasional broken leg."

Examining Magistrate Martin Trapp: The accident could have been caused by a thunder storm

Reports say a sudden storm swelled the Saxeten brook into a raging torrent, uprooting trees.

The stream flows into a river which in turn empties into Lake Brienz around 60 kilometres (37 miles) southeast of the Swiss capital, Bern.

Examining Magistrate Martin Trapp, who is investigating the accident, told the BBC there had been thunder and lightning in the afternoon and he would be looking at whether the storm could have caused the deaths.

The authorities have set up a special phone line for worried relatives on (41-31) 634-20-51.

Australian disaster

Canyoning is considered dangerous even in the best weather conditions.

The accident happened after water levels rose

It has been described as whitewater rafting without the raft and is banned in many states in America.

The tragedy comes just months after a British teenager was killed canyoning in the Blue Mountains near Sydney, Australia.