The Sichuan earthquake may eventually claim as many as 50,000 lives, the Chinese government said today, as helicopters planned aid drops in remote areas of the province.

China’s defence minister is to deploy 101 more helicopters in a desperate attempt to limit the escalating death toll as at least 40,000 people remained buried beneath the rubble following Monday’s disaster.

At least 19,500 people have died so far following the 7.9 magnitude earthquake. Rescuers bolstered by 110,000 troops and police have been digging for survivors.

Thousands of soldiers were dispatched to repair “extremely dangerous” cracks in the Zipingpu Dam in Sichuan province amid fears that many other dams were at risk of bursting and adding to the devastation.

Meanwhile 19 British tourists feared lost in while visiting a famous panda breeding area near the earthquake’s epicentre have been found alive and well, the British Embassy in Beijing said today.

A Chinese military helicopter evacuated 14 of them from Wolong and took them to Chengdu, the Sichuan capital, where they were visited by the British Ambassador Sir William Ehrman.

They were among a group of 33 tourists from Britain, France and the United States, who were flown out. The remaining five British tourists are understood to be safe and well and will be evacuated later today.

An Embassy spokesman said reports of other missing Britons were still being investigated.

Tens of thousands of people have poured down from the mountainsides of Sichuan searching for food and water as rescuers evacuated towns where tens of thousands of people are dead, buried or missing.

Helicopters began to airlift residents out of the villages of Wenchuan county at the epicentre of the earthquake which struck China on Monday, while others walked for hours into the valleys and plains to the south and east. The county is still cut off from land-based relief by landslides.

But the exodus might yet be heading into more danger, with emergency workers attempting to plug gaps in two major dams.

The Zipingpu dam, above the city of Dujiangyan with its population of 600,000, was said at one stage to be in an "extremely dangerous state" with cracks more than four inches wide appearing in its face, though the water resources ministry later said on its website that it was stable for the time being.

Tulong dam, further north on the Min river, was said by officials to be near collapse, something which would have a knock-on effect on a series of dams and power stations further downstream.

Almost 400 dams altogether were said to have been affected by Monday's earthquake – the wet and mountainous province is criss-crossed by some of China's biggest and fastest-flowing rivers.