China ? Chinese authorities prepared on Saturday to drain a swelling lake formed by a devastating earthquake, completing work on a drainage channel to divert water that threatens hundreds of thousands downstream.

Officials are expected to discharge flood water from the lake into the channel between today and Tuesday, the official Xinhua News Agency reported, quoting Yue Xi, deputy chief of the water and electricity section of the People’s Armed Police.

The lake, called Tangjiashan, formed above Beichuan town in the Mianyang region of Sichuan province when a hillside plunged into a river valley during the May 12 quake.

Chinese authorities had evacuated nearly 200,000 people by early Saturday and warned more than 1 million others to be ready to leave quickly if the lake floods.

Meanwhile, a military transport helicopter carrying 10 people injured in the quake and four crew members crashed Saturday in Sichuan province in fog and strong turbulence, Xinhua said.

There was no immediate word on survivors. A search-and-rescue mission was under way, the news agency said today.

The confirmed death toll from China’s worst quake in three decades was raised Saturday to 68,977, an increase of about 120 people from a day earlier. Another 17,974 people were still missing, the State Council, or Cabinet, said.