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A handout file photo of the Russian-owned ship MV Akademik Shokalskiy which was trapped in the ice at sea off Antarctica.ANDREW PEACOCK / AFP - Getty Images, file

A Russian research ship and a Chinese icebreaker that were stranded in Antarctica have broken free from heavy ice and no longer need to be rescued by the United States, Australian officials said Wednesday.

More than 50 scientists, researchers and tourists had to be airlifted from the Russian-owned vessel Akademik Shokalskiy after it became trapped on Dec. 24, 100 nautical miles east of French Antarctic station Dumont d'Urville and about 1,500 nautical miles (2,250 miles) south of Tasmania, Australia.

The protracted international rescue effort was itself delayed by the conditions, with blinding snow, strong winds and thick sea ice preventing the airlift until Jan. 2.

The passengers were ferried to an Australian vessel by a helicopter from the Chinese icebreaker Xue Long, or Snow Dragon, which had been on its way to help but itself became stuck in the thick ice.

Australian officials then asked United States Coast Guard ice breaker Polar Star to assist, but the American vessel was stood down late Tuesday after both the trapped ships finally emerged from the ice sheet.

“The Akademik Shokalskiy and the Xue Long have broken free from the ice in Antarctica and are no longer in need of assistance,” the Australian Maritime Safety Authority said in a statement Wednesday.

The Polar Star “has been released from search and rescue tasking,” the statement added, “and will now continue on its original mission to McMurdo Sound.”

NBC News' Marc Smith contributed to this report.