The rescue team – including two British divers – believes it picked up signs of life of Eric Establie, 45, a highly experienced French potholer who went missing a week ago in the underground gorges of the Ardèche.

They believe Mr Establie could be safe in an air pocket above an underground river some 780 metres from the cave mouth and 180 metres directly below the surface. Collapsed rocks are blocking the exit from the flooded underground gallery.

The British divers spotted the trapped man's diving gear pointing in their direction just behind the collapsed rock. "For us this is a message. Eric is saying to us: 'I'm alive, come and get me!," said Rober Crozier, a local speleological expert.

Rescuers were clearing rocks from a natural shaft leading to the spot they believe the speleologist is holed up. They were trying to bore a tunnel down wide enough to send him food and messages.

Divers have also left full oxygen tanks and a rescue lifeline by the gallery obstruction in case the stricken potholer manages to reach them.

Rescuers expressed cautious optimism about bringing him out alive. "We still don't know when he will come out. He'll maybe need to mend his equipment (before coming out with the help of other divers)," said Jean Rampon, government sub-prefect of Largentière.

Source: http://www.telegraph.co.uk