Updated

Six high school students and a teacher died after being swept away in a raging river Tuesday during an outdoor adventure course in a rugged New Zealand national park, police said.

Five survivors were rescued after the 10 students, a teachers and course instructor were carried away by rising waters in the Mangatepopo River in North Island's Tongariro National Park.

The survivors were in good condition and will be evacuated Wednesday, said police Inspector Dave White said.

"Conditions don't allow their recovery by helicopter at this time ... and we will be better placed to carry out recovery at first light," White said in a statement.

The teenagers from Elim Christian High School in the northern city of Auckland were part of a group of 40 students attending a weeklong education course at the Sir Edmund Hillary Outdoor Pursuits Center in the small town of Turangi.

Inspector Steve Mastrovich said a helicopter with night vision capability swept the river after dark.

"It looks as though there has been sudden flash flooding. An instructor was with them and they've just been caught in the wrong place at the wrong time," he told reporters.

Murray Burton, principal of Elim Christian High, said the group of 12 were on the river when they became separated from the main party.

"From what I understand they were well equipped for the journey with wet suits, life jackets and harnesses," he said. "It is a fairly standard sort of activity. I guess it was the (outdoor center's) call as to whether they should still go (out in the conditions), and I have no reason to doubt their judgment."

It was not clear whether they were in a boat or crossing the river on foot, but the group had "become separated and were swept into the water when (it) rose very quickly," he added.

"Our prayers are with the students, the teachers and their parents," school official Phil Gaze said.