Two people are dead and the wife of Gareth Morgan has miraculously survived after a major avalanche in the South Island this morning.

Jo Morgan survived the 5.30am avalanche on Mt Hicks by digging herself out of snow - and set off a locator beacon.

Department of Conservation director-general Lou Sanson told the Herald that Morgan had "done all the right things" and having her personal locator beacon (PLB) by her side "has undoubtedly saved her life".

He has been comforting his friend at Unwin Lodge this morning after meeting the rescue helicopter off the mountain.

"She's strong but shattered," he said.

"There has clearly been a large avalanche come off Mt Hicks into Harper Saddle. She has done an amazing job extricating herself. She had her PLB right close to her body which has undoubtedly saved her life. I would have to say it's a textbook recovery of getting out of an avalanche, and it's just so sad for the other two."

He told the ODT that Morgan was able to get help by getting the Rescue Co-ordination Centre involved at about 6am.

''We were on site not long after 7am but tragically too late for the other two victims.''

Police senior constable Les Andrew has confirmed a party of three people were ascending the mountain when they were caught in the avalanche.

He says the deceased are two men - both mountain guides. Newstalk ZB is reporting the two guides were both very experienced and one is believed to be German.

Les Andrew says police have begun informing next of kin and the deaths will be referred to a coroner.

Sanson said Morgan was an experienced climber.

"Mt Hicks and Torres [Peak] were the last two of the 3000ft peaks that she was trying to do – she has done 22," Sanson said.

"We're just feeling shattered. The DoC staff have been so professional in how they responded this morning and really just got in there and done the job. But unfortunately it was too late to bring the other two out."

Jo Morgan's daughter Jessi, wrote on Facebook: "Just an update that Jo is safe and back at Mt Cook village. Thanks for all your support and messages."

A major search operation was launched after the avalanche on Mt Hicks, near Mt Cook, this morning.

Rescue Coordination Centre spokeswoman Grace Loftus said the alarm was raised early this morning - by Morgan - who was with two guides.

A statement from St John says: "Given the outcome of the incident, all inquiries now have to go through police. I can confirm, though, that St John did attend with a helicopter from CHCH with an intensive care paramedic onboard and a crew on the ground."

Jo Morgan posted on Facebook yesterday that conditions had been bleak at Empress Hut the last couple of days but said a 20-hour weather window meant they would plan to leave for Mt Hicks at 2am on Wednesday.

She posted on October 28: "Heavy packs and an overnight bivy on the way got us to the inaccessible Empress hut up the Hooker Glacier.

"Light snow has been frequent. Today is a rest day after many hours following the knee deep steps and sticky snow that added an extra kg to your many upwards steps.

"Yes I wish I'd done more training, but have decided I excel in suffering."

Rescue teams and rescue helicopters raced to Mt Hicks this morning after receiving the locator beacon signal, a Rescue Coordination Centre New Zealand spokesman said.

Two helicopters, eight alpine cliff rescue people and an avalanche dog searched.

A helicopter with medical supplies was also sent from Christchurch.

Mountain Safety Council spokesman Nick Kingstone said there was a lot of snow in the mountains, with considerable avalanche danger above 18 metres.

"Even on a low danger rating day, it doesn't mean there's no avalanche risk.

"It doesn't actually take a lot of material or snow to sweep a person off their feet."

Sanson is in the region today to attend a funeral of one of the DoC staff members killed in the Wanaka helicopter crash.

DoC rangers Paul Hondelink, 63, and Scott Theobald, 59, died along with pilot Nick Wallis, 38, when their chopper crashed soon after take off from Wanaka airport on October 18.

A funeral service for Theobald, who pioneered the use of pest control dogs, is being held at Glentanner Holiday Park, Aoraki/Mt Cook at 2pm today.

"All these people are known to our DoC staff, so it's another heart-wrenching blow," Sanson today told the Herald.

"My whole purpose of being here was to really focus on Scott and give him the very best send-off we possible can just 15 minutes down the road. It's a stunning day here, but such sad circumstances."

Mt Hicks, 3198m, is a mountain in the Southern Alps within the Mount Cook National Park.

Gary Dickson, who has more than 30 years of climbing experience, said if the rescue was on Mt Hicks it was a mountain that was tricky and one of the more difficult mountain climbs in New Zealand.

The Alpinism and Ski owner operator said the climbing difficulty in Mt Cook Regional Park was scaled from one to six. The easiest route on Hicks was a 4, while there was some that were a 5.

There were several routes up the mountain, the most popular was the south face which was a series of steep climbs.

"It's steep ice climbing for New Zealand," he said. "There is an awful lot of difficult climbs there."

Avalanche Advisory New Zealand (AANZ) has warned of rapidly changing volatile spring conditions in the Aoraki/Mount Cook National Park area.

A spokesman said a high degree of caution was advised until 10am tomorrow.

Dangerous avalanche conditions, careful snowpack evaluation, cautious route-finding and conservative decision-making was essential from above 1400m, he said.

The latest advisory at www.avalanche.net.nz says there is a considerable risk of avalanches in Arthur's Pass, Craigieburn Range, Mt Hutt and Aoraki/Mt Cook.

Avalanches can happen at this time of year as the warmer temperatures, combined with rain, increased risk.

A week ago three hunters had a lucky escape after an avalanche brought snow crashing onto their tents in Fiordland, at the head of Lake Te Anau.

The incident also follows the death of Caleb Jennings earlier this month.

The 31-year-old was seriously injured while climbing near Mt Harper, in Mid Canterbury, on October 22. He died in Christchurch Hospital three days later.

Jennings had been a member of the New Zealand Alpine Team.

More than 140 people have died in avalanches in New Zealand, according to records that began to be kept in 1860.

One of the worst incidents happened in August 1863 when a massive avalanche buried a camp of goldminers in Otago, killing 41. In modern times avalanches most often claim the lives of climbers.

Another tragedy occurred on June 23, 1966, when a rescuer was killed in an avalanche during an unsuccessful attempt to rescue four climbers trapped on Mt Rolleston.

In 2015, Sydney skier Roger Greville died after being pulled from avalanche debris near the Devil's Staircase, near Queenstown.

More to come