Efforts to drain a swollen "quake lake" in southwest China have been succeeding, but a government minister warned the situation remained dangerous, state media said.
Between 400 and 500 millimetres (16 and 20 inches) of rain, well above average, was forecast to fall upstream in June and July, the Xinhua news agency reported on Saturday, citing water resources minister Chen Lei.
"This poses a challenge for the already swollen lake... Aftershocks, landslides and leakage are also threatening the lake's barrier," Chen said in quake-struck Sichuan province, according to Xinhua.
Landslides could take place on mountains above the lake, causing another 17 million cubic metres (600 million cubic feet) of rocks and earth to crash into the water, Xinhua said.
The lake's barrier, which was caused by landslides in the massive May 12 earthquake, would immediately burst and cause another disaster, according to the agency.
Troops began draining water from the Tangjiashan lake through a hastily dug channel on Saturday, to stop it from bursting its banks and emptying 220 million cubic metres of water downstream.
The lake has become one of the most pressing issues in the aftermath of the quake that struck mountainous Sichuan, killing 69,134, according to the latest toll, and leaving millions homeless.
The magnitude-8.0 quake triggered massive landslides that blocked rivers and created more than 30 unstable "quake lakes," with Tangjiashan, on the Jianjiang river, being considered the most dangerous.
Soldiers have been widening and deepening the channel to speed up drainage with the help of 30 bulldozers and excavators. They were also digging a second channel, Xinhua said.
Despite the drainage, the lake has continued to rise, adding another 30 centimetres (12 inches) over six hours on Saturday evening, according to the agency.