The death toll from China's deadliest earthquake in decades climbed to nearly 15,000 on Wednesday, as officials warned of calamities downstream from broken rivers and dams strained to bursting point. Tens of thousands of troops, firefighters and civilians raced to save more than 25,000 people buried across a wide swathe of southwest Sichuan province under collapsed schools, factories and hospitals after Monday's 7.9 magnitude quake. The official death toll climbed to 14,866, as rescuers pulled at tangled chunks of buildings for signs of life. The government sent 50,000 troops to dig for victims. Amid the overwhelming gloom, there were also moments of joy. In Mianzhu, where thousands have already been confirmed dead, about 500 people were pulled out alive from crushed buildings. Rescuers in Hanwang, a village in Mianzhu, sustained a girl with food and water as they struggled to free her from the ruins of a school. A woman eight-months pregnant and her mother, trapped under an apartment building in Dujiangyan, were freed by firefighters. "We are very happy. We have been standing here shouting for two days," said Pan Jianjun, a relative. "But there are still three more people in there making sounds." But television showed whole villages wiped out across the poor, mountainous region suggesting searchers would find many more bodies than survivors among the toppled buildings. 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". Authorities warned that dams could burst. 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, 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.