DOC was warning against tramping in the area near a hut where a woman stayed for weeks after her partner died in a fall, a Dunedin tramper says.
Police found the Czech woman living in the warden's quarters of the hut on the Routeburn Track in Otago yesterday.
She told police she had been there for weeks, after her partner died in a fall on the track in late July.
Police started searching for the woman and her partner yesterday after learning they had not been heard from since late last month.
Inspector Olaf Jensen said officers found the couple's car at the start of the track and soon after, found the woman at the hut.
The woman told officers her partner fell down a steep slope on 28 July, Mr Jensen said.
She managed to climb down to him but he died not long after and she then made her way to the hut.
She had been taken to hospital for assessment and was in good health, but "understandably upset" by everything that had happened, he said.
Search and rescue teams would return to the track later today to try to find her partner's body.
The case was "highly unusual", Mr Jensen said.
"It very unusual for someone to be missing in the New Zealand bush for such a long period without it being reported."
Officers would talk to the woman again today to try to piece together what had happened.
Dunedin tramper Barry Walker was on the Routeburn Track last weekend, before the woman was discovered, and had stayed away from Lake Mackenzie hut because of the avalanche risk on that side of the track.
"We were in three feet of snow and sinking down.
"There was snow covering, or up to the top of the track markers."
DOC's Te Anau office had been warning trampers away from the Lake Mackenzie end of the track and so it could be possible no one had made it up to the hut during August, Mr Walker said.
"That's why we didn't go in there."
The warden's hut was right next to the main hut but the woman could have remained hidden away even if someone had arrived at the hut, Mr Walker said.
"She probably got weaker and weaker and couldn't get out anyway."
Experienced tramper and guidebook author Shaun Barnett said the track - which is one of DOC's 'Great Walks' - was much quieter in winter and would have received a lot of snow during the cold snap at the start of August.
But he found it "extraordinary" that no one would have visited the hut for an entire month.
He was baffled as to how the woman had survived.
"Sometimes there might be leftover food in the warden's quarters, but that's not necessarily so. It'd be unlikely there'd be food in the main hut."
He, too, believed the woman may have ended up unable to walk out on her own.
"[Shock] would explain a few days or even a week but it's harder to explain that shock value over a whole month, unless it's something to do with she got weaker and weaker through lack of food and less and less confident about trying to get out.
"But then again it seems puzzling that there wouldn't have been at least someone coming through the track who she could have sought help from."
The track was easy going during summer but could become much more difficult in winter, he said.
The two danger points were around Lake Harris, which had bluffs below and above it, and the Hollyford face, which was a long, steep slope, Mr Barnett said.
"If it's covered in snow, your nice benched track isn't going to exist and you're going to be walking at an angle - and if that's frozen it's quite a different proposition to doing it in summer."
DOC Wakatipu operations manager Geoff Owen said the department was supporting the woman and working with police to work out exactly what happened.
Huts were open but not regularly checked by rangers during the off season, he said.
Information on DOC's website for people tramping the Routeburn Track during winter warns that conditions can be very wet and cold, and alpine areas are usually covered in snow.
"Snow and ice conditions on the Hollyford face and at the Harris Saddle can be extremely dangerous," it said. The route also incorporated "challenging and complex avalanche terrain".
The Routeburn Track generally takes three to four days to complete, with Routeburn Falls and Lake Mackenzie huts the main sources of shelter.
Both huts sleep about 50 people but do not have wardens over winter.
The Routeburn Track and the nearby Milford Track in Fiordland National Park are two of DOC's 'Great Walks' and are graded as easier tramping tracks in summer.
However, there have been several fatalities and disasters in the area over the years:
- 2014 - Yessica Asmin, visiting from NSW, dies after being swept down a river while tramping the Milford Track
- 2010 - DOC evacuates 120 trampers from the Milford and Routeburn tracks after major flooding washes out a bridge and affects others.
- 2008 - Israeli tourist Liat Okin dies after slipping on boulders after wandering off the Routeburn Track onto an emergency route.
- 2005 - German tourist Johanna Kuchelmeister drowns trying to cross Mistake Creek near the Milford Track.
- 1994 - A huge landslide near the Lake Mackenzie end of the track closes the route for months.
- 1963 - Teenagers Heather McElligott and Bryan Lamb die in a freak summer snowstorm near Lake Mackenzie.