The two mountain guides killed in an avalanche near Mt Cook died almost instantly, police say.
The men became caught in the avalanche when it struck Mt Hicks on the western side of Aoraki/Mt Cook early on Wednesday.
The lone survivor, Jo Morgan, wife of entrepreneur and former politician Gareth Morgan, managed to dig herself out and was rescued. She is safe and has been helicoptered to Christchurch.
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"I'm just so lucky to be alive. I was buried too," Ms Morgan told Newshub. "It took me nearly an hour to dig myself out and set the locator beacon off."
Mid-South Canterbury Area Commander Inspector Dave Gaskin told media the trio had reached the summit and became 'engulfed' by the avalanche on their descent.
"I think one of them was killed pretty much instantly, and one of them probably perished before the team got there."
The men, both in their 50s, are New Zealand citizens based in central Otago, but are believed to be from Germany, Inspector Gaskin says.
"These guys, although not employed by the Department of Conservation, are well-known - they're well-known through the Aoraki/Mt Cook National Park and other climbing areas, so it will have a dramatic effect."
Their bodies have been recovered and next of kin are being notified.
Westpac paramedic Wayne Ledgerwood told Newshub the men were under full CPR on their way back to Mt Cook village from the mountain.
"These victims were suffocated [by snow] because of the hypothermia, low body conditions - resuscitation is continued as far as practical."
Senior Constable Les Andrew of Twizel told Newshub the trio were roped together when the avalanche hit.
"The survivor stayed near the top of the avalanche by doing a swimming action."
He says Ms Morgan had one arm out of the snow and was able to activate the alarm.
The trio set out to summit Mt Hicks at 2am from Empress Hut.
The climb was one of the last of Ms Morgan's she had to summit to complete climbing all of New Zealand's peaks above 3000m, Inspector Gaskin says.
He says Ms Morgan is fortunate to be alive, saying "the fact two people have died indicates how lucky she is".
"She's obviously kept a really good presence of mind, she's followed her training and acted accordingly - that is really the only reason she's alive."
The climbers were all extremely well-equipped - they just found themselves in an "unlucky situation".
"A lot of people climb the mountain, but not many people climb in that area, because it's a wilderness area," Inspector Gaskin said.
"To get to Empress Hut, which is the only hut up there, it takes between 12 and 16 hours walking - so it's a long, long way in a high-altitude area."
Ms Morgan had been posting updates on her climb on Facebook.
Her daughter Jessi commented on her post earlier on Wednesday, saying: "Just an update that Jo is safe and back at Mt Cook village. Thanks for all your support and messages".
Gareth Morgan has been contacted for comment.
Department of Conservation guides made up the rescue team.
Director general Lou Sanson, who was with Ms Morgan when she made it back to Mt Cook village, told Newshub she did everything right.
He said was extremely proud of his staff who were involved in the rescue.
"My main task at the moment is to comfort Jo. She's safe and well, done a textbook recovery out of a pretty significant avalanche."
Mr Sanson was in the area heading to Scott Theobald's funeral who was one of three people killed nearly two weeks ago in a helicopter crash in Wanaka.
Many of the staff involved in the rescue knew Mr Theobald and the men killed in the avalanche, he says.
Police are investigating the incident and the men's deaths will be referred to the Coroner.