The death toll from China's deadliest earthquake in decades rose to nearly 15,000 on Wednesday as officials warned of calamities from broken rivers and dams strained to bursting point.
The official death toll climbed to 14,866, as rescuers pulled at tangled chunks of buildings for signs of life.
Tens of thousands of troops, firefighters and civilians are racing to save more than 25,000 people buried across a wide area of southwest Sichuan province under collapsed schools, factories and hospitals after Monday's 7.9 magnitude quake.
Officials have also warned of dangers from increased strain on local dams as well as mudslides on brittle hillsides where rain has been forecast over the next few days.
Two hydropower stations in Maoxian county, where 7,000 residents and tourists remain stranded near the epicentre, were "seriously damaged".
Thousands of troops are tonight fighting to plug dangerous cracks in a dam above an earthquake-hit Chinese town. Zipingpu Reservoir is upstream from Dujiangyan, which was near the epicentre of the quake.
China’s top economic planning body said today that the earthquake had damaged 391 dams. It said two of the dams were large and 28 were medium-sized.
Landslides had blocked the flow of two rivers in northern Qingchuan county, forming a huge lake in a region where 1,000 have already died and 700 are buried, Chinese state news agency Xinhua said.
"The rising water could cause the mountains to collapse. We desperately need geological experts to carry out tests and fix a rescue plan," Xinhua quoted Li Hao, the county's Communist Party chief, as saying.
The quake had also stopped a river in the stricken Mianzhu region, prompting officials to evacuate residents and drain dams, downstream, the agency said.
The government has sent 50,000 troops to dig for victims. According to the army, in Wenchuan, at the epicentre, one-third of houses have been destroyed, and more than 90 per cent damaged. Many schoolchildren were buried as they were taking an afternoon nap.
In Mianzhu, where thousands have already been confirmed dead, about 500 people were pulled out alive from crushed buildings, however.
Premier Wen Jiabao made emotional appeals to workers and comfort orphaned children. "Your pain is our pain. . . . Saving people's lives is the most important task."
The earthquake, the worst to hit China since 1976 when up to 300,000 died, has muffled upbeat government propaganda three months ahead of the Beijing Olympic Games.