Five days after the 7.9-magnitude quake, the official death toll reached almost 29,000, with 148,000 soldiers and police, involved in the relief operation.

But there were signs that survivors may still be clinging to life, buried under tons of rubble.

Rescuers worked through the day - using saws, drills and their hands - to free one woman pinned alive under a crumpled six-story apartment building in Longhua.

Bian Gengfeng, 31, was taken away by medics covered in mud and dust after 124 hours in the rubble.

Rescue teams from South Korea, Singapore and Russia joined Japanese specialists. But the 10-member team from the British International Rescue Corps (IRC), standing by in Hong Kong, stood down after Chinese officials there refused to grant the necessary visas.

The team, including a fireman, a landscape gardener and a structural engineer, is equipped with a miniature camera, sound location devices and a carbon monoxide analyser, but they will now return to the UK.

Spokeswoman Julie Ryan said they had to respect the decision of the Chinese authorities who told them they were unable to co-ordinate foreign nationals.

She said: "The chances of finding people under the rubble after five or six days are rapidly diminished but it's still possible. Over the next few days I think we will still see people being pulled out. They have to have certain factors in their favour, like not being injured and having access to rain water to drink."

Ms Ryan, who took part in the rescue effort after the 2005 Pakistan earthquake, said in "miraculous" cases it was possible for survivors to be found after almost two weeks.