Landslide lake

Al Jazeera's Melissa Chan, reporting from Zhouqu, the county seat and the hardest-hit area, described an area surrounded by treeless mountains, due in part to logging efforts.

"[A] combination of natural disaster but also environmental damage," she said. "Lots of timber comes from here."

She said she had seen at least four corpses pulled from the landslide on Tuesday, adding that the up to one metre high mud there was "like quicksand".

The last reported survivor was found on Monday morning, but rescue workers said they were still finding signs of life.

A blockage caused by the landslides in the Bailong river worsened the devastation after a newly created 3km-long lake overfilled and sent massive waves of mud, rocks and water crashing down into Zhouqu County.

But reports said engineers had now lowered its water levels, using controlled explosions to create a channel and funnel off some of the water.

State broadcaster CCTV has said that around 45,000 people had been evacuated from the area.

Wen Jiabao, the Chinese premier, visited the area on Monday and promised to help the survivors.

"The key tasks and challenges are expanding the scope for search and rescue, dealing with the barrier lake (caused by mudslides) in a  timely and scientific manner, cleaning the sludge and resuming the supply of drinking water," Wen was quoted by the official Xinhua  news agency as saying Monday.

He said that relief efforts would continue as long as hopes of survival existed.