Chinese troops on Saturday eased pressure on a swelling "quake lake" threatening hundreds of thousands of people, but a smaller lake burst its banks in a show of destructive force.
The May 12 earthquake centred in the southwestern province of Sichuan, which killed more than 69,000 people, also triggered landslides that blocked rivers and created over 30 such lakes, raising fears of lethal floods if the new "dams" suddenly burst.
Hundreds of troops were mobilised to dig a channel to release water from the Tangjiashan quake lake, the largest.
Early on Saturday some of the pent-up water began to flow out, and officials sounded relieved.
"We don't see any danger to downstream at present," Hu Peng, an official in the command centre overseeing the lake relief effort, told Reuters. "We're paying very close attention, but for now the flow doesn't indicate any threat."
But at Majingxiang, downstream from Tangjiashan, a quake lake burst on Friday, spraying out a torrent of rock and gravel in a 500-metre-long tongue that blocked the road to the area.
A construction worker said he and others scrambled for their lives uphill when the lake they were trying to relieve burst through the barrier formed by a landslide caused by the quake.
"We were releasing water through a man-made channel about two metres wide, but then it suddenly gave way and there was this roaring sound and we ran up the side of the hill," said Chen Youfu, smoking a cigarette as he looked down on the debris.
CORPSES UNCOVERED
Corpses were exposed in the rock and gravel left by the surge, as well as four earth-moving vehicles tossed like toys upside down or onto their sides.
Chen and other workers and medical staff at Majingxiang said the three bodies uncovered were of people killed in the quake, not victims of the Friday collapse.
Police rescued several villagers who were caught in the surge downstream, the Ministry of Public Security reported. The report did not mention any deaths.
The backed-up lakes are merely one of the hazards and problems burdening millions of people living in tents nearly four weeks after the earthquake devastated their homes -- along with grief, heat, rain, disease, and gnawing uncertainty.
"What I'm most worried about is what happens next. We lost everything we had and we don't know what we'll get back," said Liu Shiyou, 57, a farmer from the nearby area of Chaping.
Chinese Premier Wen Jiabao said the lake threat had to be solved urgently.
"The longer the delay, the greater the pressure created by the quake lakes, with safety threats multiplying and new hazards more likely to arise," Wen said on Friday near Mianyang, a threatened downstream city.
More than 250,000 people have been evacuated from quake-ravaged areas of Beichuan, Mianyang and Jiangyou. There are contingency plans to move up to 1.3 million if the Tangjiashan dam fully breaks.
The 220 million cubic metres of water caught in the Tangjiashan quake lake also threaten a major oil pipeline. Engineers have developed an emergency plan to use a temporary supply line if the pipeline ruptures, Xinhua reported.