Six high school pupils and their teacher were swept to their deaths in a freak flash flood at a wilderness gorge in New Zealand.
Five other students were plucked to safety from the torrent in the Mangatepopo River that trapped the hikers in the Tongariro National Park on New Zealand's North Island yesterday.
School principal Murray Burton said the deaths yesterday were a "tragedy which defies belief". Prime minister Helen Clark expressed "profound sympathy and shock".
The six students who died were 16 and the teacher was 29.
Officials said there was no apparent warning to the group when the river rose to about four times its normal water level in the narrow gorge within half an hour.
The teenagers from Elim Christian High School in Auckland, New Zealand's largest city, were part of a group of 40 pupils attending a week-long course at the Sir Edmund Hillary Outdoor Pursuits Centre in the small town of Turangi.
The course involved navigating the gorge by swimming, clambering over rocks and hiking.
Mr Burton said the hiking group was well equipped with wetsuits, life jackets and harnesses and were in the care of an experienced guide. Those swept away were in a group of 12 that became separated from the main party.
District Police inspector Dave White said he understood the students were on a team-building exercise traversing the river when they were overcome by the rapidly rising water levels.
"It's too early to say exactly what happened as the matter is under investigation," he said.
Police inspector Steve Mastrovich said a helicopter with night vision capability swept the river after dark yesterday looking for signs of life.
"It looks as though there has been sudden flash flooding ... and they've just been caught in the wrong place at the wrong time," he said.
Ms Clark a mountaineer and wilderness lover, moved a condolence motion in parliament.
"This is every family and school's worst nightmare," she said.
"To have this happen when young people are out doing a healthy and normally very enjoyable activity, and it turns into a terrible tragedy."
Pupils at the school were told of the tragedy at a special assembly, where "ripples of shock and tears moved around the hall" a witness said.
Many pupils and family members were in tears and stood in groups hugging after arriving at the school for the assembly. Bunches of flowers were piled up outside the assembly hall.
New Zealand's spectacular and rugged wilderness is world famous, and many of the country's inhabitants pride themselves on their close connection to it. Mountaineering, hiking and sailing are common pursuits among the nation's 4.2 million people.
Grant Davidson, chief executive of the centre that organised the trip, said the conditions appeared safe and there was no warning of the heavy rain that quickly developed in the area.
"I am comfortable this was a normal activity we had with this age group in these sort of conditions," he said. "Obviously if we had known or predicted about the pulse of water we would not have been there."
Clark praised the centre's strong reputation for working with young people in New Zealand's wilderness.
Police and the adventure company said they would further investigate whether there had been any safety breaches.