The group of trampers who got lost on Mt Tongariro have been safely rescued, with one in hospital for further treatment.
The four Auckland trampers, aged in their 20s and 30s, were all inexperienced but generally well prepared for their trip. Two became separated after going on to Oturere Hut.
Senior Constable Barry Shepherd said it appeared that a late start and becoming separated meant the trip didn't quite go to plan.
He's now calling on trampers to be more vigilant and not be afraid to call for help or turn back if they realise they're getting into trouble.
"Due to its popularity, people seem to underestimate the challenge of the Tongariro Alpine Crossing.
"Getting caught in a blizzard while not sticking together caused the group to inadvertently separate. Two of the trampers went ahead of the other two, a couple, as one was having trouble with their crampons," Shepherd said.
"It's easy to speed ahead if you're experienced but tramping groups should always accommodate the abilities of the slowest member of the group, not their own.
"If you start together, finish together."
As for what happened, Shepherd said the two who were ahead carried on toward Oturere Hut after waiting for a period of time.
"Meanwhile, the couple were still walking but got concerned when, after three hours of walking on a track that was supposed to take one and a half hours, they had not arrived at the hut.
They stopped and called for help at 8.40pm as weather conditions and their own physical conditions deteriorated."
A helicopter was not able to reach the area due to cloudy conditions so a search and rescue team was sent in on foot from near Ketetahi Hut.
Meanwhile, the two trampers also became concerned when their friends had not arrived by midnight and called police.
They eventually went out and found the pair and the woman was carried back to the hut due to hypothermia.
"Our key concern with the planning of their trip was the timing. They didn't get to the top of Tongariro until 5pm, when it was almost dark, due to their late start," said Shepherd.
"Then, when they got in trouble, they didn't call for help until it was very dark and one tramper was unable to walk. We'd hope people would call for help sooner."
LandSAR volunteers reached the group at approximately 2.45am today and stayed the night with them at the hut.
"All their clothing was wet so although they had all the right gear, they didn't have it in waterproof packing. They had adequate food, drink and clothing, until the blizzard hit - a highly likely event at this time of year," he said.
"We've asked them to just share their learnings with their friends who are keen on the outdoors, to ensure others don't repeat their mistakes.
"The group are thankful to the rescuers and are being quite reflective at this point.
"New Zealand's outdoor life is beautiful and exciting but unfortunately it can be extremely unforgiving."
He urged trampers to give themselves extra time to make it to their destination or turn back if necessary.