Image caption The Chinese vessel, Xue Long, has expressed fears that it has also become stuck in the ice

The Chinese ice-breaker that helped rescue passengers stranded on the Akademik Shokalskiy vessel in Antarctica may now itself be stuck.

An Australian ice-breaker carrying the rescued passengers has been placed on standby in case the Chinese ship, Xue Long, needs assistance.

On Thursday, a helicopter from Xue Long transferred 52 passengers from the Shokalskiy to the Aurora Australis.

The Shokalskiy has been trapped by thick floes of ice since 24 December.

"Xue Long notified Amsa [the Australian Maritime Safety Authority]... this afternoon [that] it has concerns about their ability to move through heavy ice in the area," Amsa said in a statement.

"[Xue Long] will attempt to manoeuvre through the ice when tidal conditions are most suitable during the early hours of 4 January," Amsa said, adding that there was no immediate danger to the crew on the Xue Long.

The Australian Aurora Australis has been asked to remain in open water nearby as a precautionary measure.

BBC reporter Andrew Luck-Baker is on board the Australian ship: "The irony of the situation is that the Xue Long was originally summoned to break a clear route through the pack ice to the smaller Russian vessel. That was not possible and the large icebreaker is now trapped itself.

"As a precautionary measure, the Australian icebreaker has been put on standby to assist the Xue Long, if needs be. All the vessels involved in this drama are within a sea area of East Antarctica that is claimed by Australia. Hence, the coordinating role lies with the Australian Maritime Safety Authority."

Image caption All 52 passengers on the Shokalskiy were rescued and transferred to the Aurora Australis on Thursday

Image caption A helicopter from the Chinese Xue Long transported the passengers

Image caption The Shokalskiy had plenty of stocks and was never in danger

It is the latest twist in what has become a complicated rescue operation in the Antarctic.

The Akademik Shokalskiy, a Russian research vessel, became trapped by thick floes of ice driven by strong winds, about 1,500 nautical miles south of Hobart - the capital of the Australian state of Tasmania.

The vessel was being used by the Australasian Antarctic Expedition (AAE) 2013 to follow the route explorer Douglas Mawson travelled a century ago.

Several attempts to break through to the ship by sea - by the Xue Long, Aurora Australis and French-flagged L'Astrolabe - failed because of the thickness of the ice.

On Thursday, a helicopter from the Xue Long managed to fly the Shokalskiy's passengers and researchers in groups to an ice floe next to the Aurora Australis.

The Return to Mawson's Antarctica The 2013 Australasian Antarctic Expedition repeats scientific investigations made by Douglas Mawson and his team between 1911 and 1914

Andrew Luck-Baker and Alok Jha are reporting on the expedition for Discovery on the BBC World Service

Listen to Part One, Part Two and Part Three of their story, or get the Discovery podcast

They were then ferried to the Aurora Australis by a small boat.

Members of the AAE have paid tribute to the Chinese captain, Jianzhong Wang, and his crew.

Prof Tracey Rogers, a marine biologist at the University of New South Wales, said: "The Chinese captain is an incredible ambassador for his country."

Prof Rogers also praised the helicopter evacuation team that made five separate flights to ferry the AAE members from the stranded Shokalskiy to a makeshift helipad close to the Aurora Australis.

"Under really difficult circumstances, they were efficient, fast and so well coordinated," she said.

"Those Chinese guys are heroes," added Nicole De Losa, head of Art at Hornsby Girls High School in Sydney.

"They made what could have been a frightening experience so quick and easy for us. Without them, we would still be stranded."

Prof Chris Turney, co-leader of the AAE 2013, said he was sorry to hear that the Xue Long was now in difficulty: "We are hoping that they, along with the crew of the Shokalskiy, will be free as soon as possible".

Early on Friday (GMT), the Aurora Australis was reported to be making steady progress through the pack ice towards an area of clear water.

Once there, its orders are to hold position, rather than proceed westwards directly to the distant Australian Antarctic base of Casey.

Our correspondent says the area will experience a particularly high tide on Saturday (4 January) at about 0400 GMT.

"The extra vertical forces on the ice floes may help to crack and weaken the consolidated pack around the Xue Long, giving it new opportunities to navigate out of the ice.

"The Aurora will wait until the effect of the high tide on the Xue Long's situation becomes clear," Andrew Luck-Baker explained.

"If the Chinese vessel can escape the pack, the Aurora will continue on its way to Casey.

"If the Xue Long remains trapped, the Australian vessel will maintain its position until there is a new alternative plan agreed."

There are 111 individuals on the Xue Long and 22 remaining crew on the Shokalskiy.