A search has begun for a plane carrying three Canadian crew members that went missing in bad weather on a flight over Antarctica.
New Zealand rescue authorities said the emergency beacon of the Twin Otter aircraft was activated while on its way to the Italian Antarctic base on Wednesday.
The Rescue Co-ordination Centre New Zealand said the beacon was transmitting from the Queen Alexandra Range, which
lies in New Zealand's rescue zone, and RCCNZ was co-ordinating the search with co-operation from US authorities at the McMurdo Antarctic station.
"Weather conditions are extremely challenging," said John Ashby, search and rescue mission co-ordinator.
"There are winds of 90 knots at the site, and conditions are forecast to worsen with snow becoming heavier."
The US National Science Foundation, NSF, said the plane belonged to Kenn Borek Air, a Canadian firm based in Calgary that charters aircraft to the US Antarctic programme.
It said the plane was flying a logistical support mission from the NSF's Amundsen-Scott South Pole Station to Terra Nova when it went missing.
The RCCNZ said a US Hercules had flown over the area where the plane was believed to be but failed to find any sign of it.
A second Twin Otter was scheduled to set out from McMurdo on Thursday morning, working with a helicopter from New Zealand's Scott Base, which would set up a camp and try to reach the area when weather conditions eased.
Steve Rendle, RCCNZ spokesman, said there were hopes the three men, whose names have not been released, were still alive.
"If the beacon is operating, which it is, that's a good sign as a heavy landing can tend to prevent the beacon working, so that's a positive sign at this stage," he told Radio New Zealand.
The plane was equipped with survival equipment, including mountain tents, and supplies sufficient for five days, RCCNZ added.