KEY POINTS:
Rescue teams are hoping for a break in the weather this morning to allow a search for six missing climbers on Aoraki Mt Cook to resume.
The condition of the climbers, believed to be Australians, is unknown, but extreme avalanche danger and snowy conditions on the mountain have hampered efforts to find the group.
Authorities were first alerted that the climbers were in trouble when an emergency locator beacon was activated at 10pm on Thursday.
The beacon continued to sound yesterday and brief aerial searches conducted in the afternoon narrowed its likely location to the Metelille Glacier area.
Land search and rescue teams have been unable to get into the area because of the avalanche risk, but three helicopters will fly in at dawn if the weather improves.
Even if the helicopters are able to accomplish their task, a climbing and rescue expert with more than 16 years' experience at Mt Cook said conditions facing the pilots and searchers on board would be extremely risky.
Mountain Guides Association president Aaron Halstead, who was head of the Mt Cook rescue team until last year, said when the avalanche risk was extreme, the area was best avoided altogether because any movement could trigger an avalanche.
"Even putting a helicopter in there is going to require some very careful thought about where to put the helicopter down," he said.
Mr Halstead, now based in Queenstown but on standby if extra searchers are needed, said the Metelille Glacier was a large area where snow loaded in from a southerly direction. "It certainly is quite an avalanche-prone slope."
If the climbers are the Australian group, they set out on Saturday after recording their intentions at a Department of Conservation office to traverse Annette Plateau from Barron Saddle to Mueller Hut.
DoC said the group was equipped with a locator beacon, but the Rescue Co-ordination Centre was still unable to confirm last night whether the signal was activated by this group or others on the mountain.
"This is a popular climbing area so there could well be another group or groups in that area who simply have not filled out the intentions book and have a beacon and have set that off," centre spokesman Ross Henderson said. "We can't make any assumptions really at this point."
Mr Henderson said it was difficult to speculate about the condition of the climbers because the nature of their distress and the exact location of the beacon signal was unknown.
The beacon was an older-style model which did not provide the Rescue Co-ordination Centre with registration details.
Such beacons also give only approximate positional information.
A fixed-wing aircraft conducted a low-level sweep of the area where the beacon was believed to have been activated, and a helicopter was able to narrow the area during a brief respite in the weather at 2pm. But it was forced to turn back when conditions closed in again.
Specialist search and rescue teams as well as alpine experts from DoC, police and other agencies, are on stand-by to try to rescue the climbers.
Mr Halstead, 36, was forced to spend eight days in a snow cave on Mt Cook with three others about 15 years ago.
He said that if the missing climbers were well equipped and knew how to build a snow cave, they could survive "completely fine".
