The search for survivors of China’s worst earthquake in 30 years became more urgent today as the predicted death toll rose to 50,000 and Chinese officials admitted that finding anyone still alive would be a “miracle”.

Zhang Zhoushu, the vice director of the state-run China Earthquake Disaster Prevention Centre, said: "As the destruction was severe and people were buried somewhere deep below ground, there's real trouble.

"If there are some survivors under such conditions, it would be a matter of luck or a miracle."

More than 19,500 people have been confirmed dead after Monday’s 7.9-magnitude earthquake in southwest China, a rise of 5,000 on yesterday's official figure.

It was reported on state television today that the government now believes this figure could reach 50,000. More than ten million people have been directly affected.

Wen Jiabao, the Chinese premier, today ordered 30,000 more troops and 90 more helicopters into the region. There are now 116,000 People’s Liberation Army officers and armed police working day and night, digging through the rubble with their bare hands, to reach survivors.

The remote areas of Sichuan province, Qingping, Jinhua and Tianchi, remained inaccessible and 500 troops were dispatched on foot to try to reach the 20,000 residents believed to be buried there.

More than $383 million of aid has been donated, by other nations, by international organisations and by individuals including China’s star basketball player, Yao Ming, who gave $214,000 and half a million yuan to the Red Cross Society of China.

The Chinese public has donated $125.4 million, as well as thousands of hammers, shovels and demolition tools in response to an rare appeal by the Chinese Ministry of Industry and Information for basic rescue equipment.

The military has made large-scale air drops of 50,000 food packages, 54,000 articles of clothing, 25,000 pairs of shoes and 5,000 blankets.

The day did see a few miracles. In the devastated town of Dujiangyan in Sichuan, a 62-year-old man was pulled from the debris after an all-night search. Onlookers cheered and took photos with their mobile phones. And in Yingxiu, a town at the quake's epicentre where almost 8,000 people have died, rescue workers pulled an 11-year-old girl out of the rubble, 68 hours after her school crashed down on top of her.

There was good news too for the families of 19 British tourists, found safe but trapped at the Wolong giant panda reserve near the epicentre of the earthquake. After three days sleeping in their tourist coach, the travellers were today being airlifted to a hotel where they could get a bath and a meal.

But as the rescue efforts were ramped up, a new threat emerged in the form of creaking and cracked dams, reservoirs and hydropower stations across the quake zone.

It was reported that authorities had found "dangerous situations" at more than 400 reservoirs – two of them major – across the five provinces affected by the earthquake. China’s water resources minister warned that those living in the quake zone could face “secondary disasters” unless they were secured.

"China faces prominent problems in safety and flood prevention at reservoirs, hydropower stations, dammed lakes and other facilities in the quake zone," the minister, Chen Lei, said.

"This is especially given the large number of reservoirs in Sichuan province, the extensive damage the quake has caused them and that the level of danger is not clear.”

Despite the increasing severity of the situation, China has so far let in just one foreign rescue team. The Japanese group of around 30 firefighters, police and coastguard workers flew to the country today and hopes to reach the disaster zone tomorrow. A second group of 30 more workers with rescue dogs will follow a day later.

But China has already refused offers of help from Australia and South Korea, and a Chinese foreign ministry spokesman today refused to be drawn on whether any other foreign aid teams would be allowed in.

"We will, according to the actual situation and the receiving capability in the localities, give serious consideration to the request of foreign rescue teams,” he said.

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