This follows the death yesterday of a 60-year-old alpine skier who was buried in an avalanche while skiing at the Ragged Range, near Methven.
Two ski guides worked furiously to dig out two other buried tourists.
The avalanche came a day after two ski guides at the Remarkables Ski Area near Queenstown were taken for a wild ride down the mountain by an avalanche after they set off avalanche-control explosives.
The man who died yesterday in Mid Canterbury, believed to be aged about 60 and an Australian tourist, was one of a group of five - three tourists and two guides from Alpine Guides - who went skiing in the Ragged Range yesterday despite a high risk of avalanche in the area.
"The guide has skied down and stopped and waited, then the three clients have skied towards him and an avalanche has been triggered, burying all three clients," Senior Constable Brent Swanson said.
The two guides dug them out but were unable to revive the man who was buried the deepest in about a metre and a-half of powered snow, despite only taking six minutes to reach him, he told Radio New Zealand.
The other two tourists were prominent South Yarra real estate agent John Castran (53) and his son Angus (23).
Lachlan Castran (25), who is also a real estate agent, said his father and brother were holidaying in New Zealand.
"Dad is in a stable condition. It was a significant, life-threatening avalanche but they were rescued and got out of there."
It is believed Angus was not trapped under the snow but his father was, and used his tongue to keep snow away from his nose so he could breathe.
The avalanche hit about an hour after warnings were issued for the Southern Alps by the Mountain Safety Council, which said significant amounts of snow had fallen, creating "slab avalanche conditions".
Large avalanches have tumbled down valleys in the Mackenzie Country and near Mt Cook village in the past two days and back-country areas of the Southern Lakes skifields were classified as high risk for "large, catastrophic" avalanches.
Skiers and snowboarders were advised to stay clear of the areas, particularly above 1700m.
The Remarkables has received more than 40cm of snow in the past week, while Coronet Peak was blanketed by more than 28cm in the 36 hours to noon yesterday.
The safety council said the snow pack was weakly bonded in most places, meaning natural and human-triggered avalanches were likely.
Back-country skiing and travel should be restricted to "low-angled areas", and it warned areas at the bottom of slopes could also be hazardous.
People needed to be aware of avalanche run-out zones, should not travel alone in the back country and should ensure every member of a party carried safety equipment and knew how to use it.
The new snow and wind had combined to create a "very dangerous situation" the council said.
Two staff from the Remarkables Ski Area were involved in an incident while carrying out avalanche control work on Thursday.
Neither was injured.
Manager Ross Lawrence told the Otago Daily Times the pair were "taken out for a slide" while they were setting off explosives to release the unstable snow.
"They were right at the top [of a ridge] letting off explosives. It was considered a safe place, but because of weight and loading below them it pulled out."
The two men "rode" the avalanche down about 75m.
"That's doing a controlled, routine blast . . . it just emphasises how serious it is in the back country," Mr Lawrence said.
Anyone entering the back country "enters at their own risk" he said.
In the Wanaka area, Treble Cone ski patrol staff were kept busy yesterday morning conducting avalanche control work.
Avalanche status
Treble Cone: Extensive control work carried out - negligible risk of danger from avalanches within ski area boundaries.
Cardrona: Patrol staff have checked field's upper slopes and access road - no risk of avalanches within boundaries.
Snow Farm and Snow Park: No risk of avalanche danger.
Remarkables: Extensive control work within boundaries - up to 14 avalanches on Thursday. Minimal risk within controlled boundaries.
Coronet Peak: Extensive checking and control work. Minimal risk within boundaries.
