More torrential rain is sweeping towards the region of north-west China hit by a massive landslide, forecasters warn.
More than 700 people are now known to have died and more than 1,000 people are still missing in the remote mountainous area of Gansu province.
The BBC's Chris Hogg in Gansu says three days of torrential rain are due.
Meanwhile, specialists in epidemic prevention have been sent to the area as fears of disease spread.
At least three villages in remote Zhouqu county were levelled by an avalanche of mud and rocks triggered by rain on Saturday.
Now rescue teams fear the fresh storms could not only hinder work to find survivors but also trigger fresh landslides.
Soldiers have been blasting through debris which partly dammed the Bailong river, lowering the water level of an unstable lake created by the landslip.
Chinese Premier Wen Jiabao urged rescuers to hurry before the weather worsened, but he acknowledged the task would be difficult.
"We must fully realise the difficulties for the search and rescue work," he was quoted by the official Xinhua news agency as saying.
"You must race against the clock and spare no efforts in saving lives."
Six specialists in epidemic prevention have been sent to the area amid growing fears that contaminated water could spark an outbreak of disease, Xinhua reported.
Yang Long, a doctor running a makeshift clinic at a Zhouqu school, told the China Daily he had already treated several adults and children for diarrhoea.
"Unhealthy drinking water and food mainly caused the disease and we need more medicine," he said.
Our correspondent says authorities face a growing problem of where to house survivors. More than 1,000 homes were damaged or destroyed and another 3,000 flooded.
More than 4,000 tents have been sent to Zhouqu county, but the mountainous terrain means there is little open space to set up camps. So far just 100 tents have been erected, he says.
Hopes of finding many more survivors in the buried buildings were fading on Wednesday.
A 52-year-old man was pulled alive from the rubble on Tuesday, more than 50 hours after the disaster, and other rescue teams say they have heard "very faint" signs of life elsewhere, state media reported.
