Wreckage of crashed helicopter found in East China Sea

"The water is muddy and it is getting dark, which increase difficulties for the search," Sun said. "We have to redouble the efforts and use advanced equipment."

The ship-based helicopter was rented by the Xuelong, or "Snow Dragon," which was moored at a Shanghai dock at the time of the accident. The helicopter crashed just a minute after taking off from the vessel, according to the China Marine Search and Rescue Center.

"Thick fog shrouded the sky when the crash happened," said a spokesman with the Shanghai frontier defense inspection authorities.

But the exact cause of the crash is yet to be determined.

Carrying 140 scientists, technicians and crew, the Xuelong left Shanghai in October for a 173-day trip, the longest in China's Antarctic expedition history.

The expedition team had successfully erected a new research station at Dome Argus (Dome A), the pole's highest icecap at 4,093meters above sea level.

They left China's Zhongshan Station for home on March 9 and arrived at Shanghai on April 10.

Editor:Liu Anqi