Search and rescue workers made visual contact with the plane's crash site late Friday night Mountain Time and the mission has now become a recovery effort.
The plane's operator, Calgary-based Kenn Borek Air, said in a written statement that the scene of the crash appeared to search and rescue crews to be "not survivable."
A New York National Guard Hercules aircraft first made visual contact with the overdue plane, the statement said.
"The sighting was confirmed approximately thirty minutes later by a Kenn Borek Air Ltd. Twin Otter aircraft deployed in a search and rescue role.
"The crew of the SAR Twin Otter reports that the overdue aircraft impacted a steep snow and ice-covered mountain slope.
"No signs of activity are evident in the area surrounding the site, and it appears that the impact was not survivable," the statement said.
A spokesperson for the company said the families of the victims have been notified.
Diane Ablonczy, Minister of State of Foreign Affairs, offered her condolences to the families and friends of the victims in a statement released Saturday.
“On behalf of Canada, I sincerely thank the New Zealand, U.S., Italian and civilian search and rescue teams for the valiant efforts they have made over the last several days to locate the missing plane," she said.
“Canadian officials will continue to work closely with local authorities in New Zealand."
Searchers unable to land at site
The search and rescue Twin Otter was unable to land at the crash site after making visual contact due to the challenging terrain and ongoing weather conditions.
Helicopter crews and mountain rescue experts will attempt to access the site over the next nine hours during a break in the weather.
New Zealand Rescue Co-ordination Centre had been organizing the search with the help of Canadian and U.S. authorities.
But fierce winds, snow and low cloud cover hampered search efforts since the plane went down near the northern end of the Queen Alexandra mountain range, some 450 kilometres from the South Pole.
The pilot has been identified by friends as Bob Heath of Inuvik while media reports have identified a second crew member as Mike Denton, a newlywed from Calgary whose photographs of planes appear on the Kenn Borek website.
The third crew member had not yet been identified.
The missing plane had been transmitting an emergency beacon signal since late Wednesday, local time, alerting rescuers to the plane's exact co-ordinates, but the battery appears to have since died.
Rescuers pinpointed the plane to be halfway between the South Pole and McMurdo Station, a U.S. research facility in Antarctica.
The missing plane had been flying from the South Pole to an Italian base in Antarctica's Terra Nova Bay. A spokesman for the U.S. National Science Foundation has said the flight was in support of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development.