A helicopter has begun rescuing passengers stranded on board a research ship stuck in Antarctica.

Professor Chris Turney, who is on board the Akademik Shokalskiy, has tweeted that a Chinese chopper had reached the stricken vessel, before the Australian Maritime Safety Authority confirmed some details of the operation.

AMSA has received confirmation that 48 passengers from the Akademik Shokalskiy are now on board the Aurora Australis.

— AMSA News (@AMSA_News) January 2, 2014

Take off! second team gone. Looking good. #spiritofmawson Alok Jha https://t.co/wdrtEYbKPq

— Chris Turney (@ProfChrisTurney) January 2, 2014

The Australian Maritime Safety Authority (AMSA) estimates the rescue of the ship’s 52 passengers, including scientists, tourists and journalists, will take at least five hours, depending on the weather.

Earlier today, the rescue mission was delayed due to dangerous sea ice conditions.

Rescuers are using the chopper to ferry passengers back to the Chinese icebreaker Xue Long.

A barge will then be used to transfer them to the Australian icebreaker Aurora Australis.

The 74 people on board the Akademik Shokalskiy had been retracing Sir Douglas Mawson’s Antarctic expedition and conducting scientific research before sea ice stopped them in their tracks.