Heavy rain has hit the county in north-western China that was devastated by landslides, as the death toll from Saturday's disaster continues to rise.
Officials said the number of people known to have died in Zhouqu, when mud and rocks engulfed buildings, now stood at 1,117, with 627 others missing.
Forecasters have warned three more days of rain lie ahead for the remote area, prompting fears of further landslides.
Meanwhile, experts have arrived there to help prevent an outbreak of disease.
At least three villages in Zhouqu county, in Gansu province, were levelled by mud and landslides triggered by rain on Saturday night.
Now rescue teams fear the fresh rain may not only hinder work to help survivors but also cause further landslips in the mountainous area.
Heavy rain was already said to be falling in Zhouqu, and up to 90mm (3.5in) of rain was forecast for Friday, the National Meteorological Centre reported.
It said that the chance of more landslides was "relatively large".
Soldiers have been using explosives to blast through debris that partly dammed the Bailong river and created an unstable lake, which eventually overflowed and sent a wave of water engulfing the town of Zhouqu early on Sunday.
A 1km (0.6-mil) long drainage channel was bringing the water level down, the official Xinhua news agency quoted the vice-minister of water resources as saying.
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 said.
"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.
The BBC's Chris Hogg in Zhouqu says the 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, our correspondent says.
Hopes of finding many more survivors in the buried buildings are fading, he adds.
On Wednesday, a 50-year-old man was rescued from a flooded hotel located inside the barrier lake formed by landslide debris.
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.