BEICHUAN COUNTY, China (CNN) -- Chinese soldiers and engineers dug a spillway from an earthquake-created lake that was threatening to burst its banks in the central county of Beichuan, state-run news agency Xinhua reported Sunday.
Meanwhile, a military helicopter carrying 10 people injured in the disastrous earthquake and four crew members crashed Saturday afternoon in Wenchuan County, state media reported. The helicopter encountered turbulence and fog before the crash. There was no word on injuries or fatalities, and a search and rescue operation was underway, Xinhua reported.
Wenchuan County in Sichuan Province is considered the epicenter of the magnitude-7.9 earthquake that struck on May 12.
The diversion project, which included a 475-meter (517-yard) channel up to 10 meters (33 feet) wide, was completed at 10 p.m. (10 a.m. ET) Saturday, said Liu Ning, chief engineer of the Ministry of Water Resources and the project's deputy director, Xinhua reported.
Tangjiashan Lake was created when a landslide caused by the earthquake dammed Jianjiang River.
By Saturday night, about 135,500 cubic meters of mud and rocks had been removed from the lake, and the plan to use explosives to blow away the blockage was abandoned because of the channel's completion, Xinhua cited Liu as saying.
According to the plan, the lake -- which has been rising about 1.6 meters daily and was seven meters from the top of its naturally-formed dam -- would spill into its man-made canal between now and Thursday. Watch what engineers and soldiers faced »
Workers hope the spillway will allow the water to bypass Beichuan town.
Farther downriver, in the town of Mianyang, Communist Party chief Tan Li -- head of the city's quake control and relief efforts -- renewed an order that 1.3 million people living downstream from Tangjiashan Lake be evacuated to higher ground.
The lake in Beichuan County is the largest of several "quake lakes" created by the earthquake nearly three weeks ago.
Authorities were concerned that the lake could burst its banks or that another aftershock or earthquake could rupture the earthen dam and cause a sudden flood of water on the communities downstream.
The project to divert the water took nearly a week. It will be Wednesday or Thursday before authorities know whether their emergency operation is successful, a commander said.
Some of the mountains overlooking the region's rivers are now bare and brown where landslides wiped them clean of their tree-covered sides. Rocks can still be heard falling from the mountains.
Because the region is so remote -- most of the roads were cut off by landslides -- the government has brought the equipment and personnel in with Russian military helicopters.
Another challenge is the weather. The commander said some members of the Chinese army have resorted to walking to the site, carrying fuel on their backs, because the helicopters were unable to fly in the fog and rain.
Many of those who have already left have been living in tents after losing their homes in the earthquake, forcing them to pick up and move again -- some for the third time.
After clearing out of one area, people left their tents and tarps standing, saying they hope they will be able to return there.
The government told frustrated evacuees that they were creating a safer place for them to stay. However, the residents said the government-created site is not as desirable as the site they are being ordered to leave. They say they would like to return once floodwaters recede.
The official death toll from the quake rose 199 from Friday to Saturday, reaching 68,977, with another 18,618 people missing.
CNN's Wilf Dinnick and Samson Desta contributed to this report.