Yaks Threaten China's 'miracle' Train Line

The safety of passengers on the world's highest - and newest - railway is threatened by cracks, yaks and shifting sands, the Chinese government has admitted.

Less than a month after the opening of the line across the Himalayas to Tibet, it has become unstable in places because the foundations are sinking into the permafrost, railway ministry spokesman Wang Yongping, told the Beijing News today.

Crossing the rugged Qinghai plateau and climbing to 5,072 metres (16,640ft) above sea level, the $4.2bn (£2.3bn) railway was hailed by president Hu Jintao as an engineering miracle for the world. But it was always likely to be harder to maintain than to build.

The line depends on coolants to stop the ice upon which it rests from melting. But global warming has raised temperatures in the mountain region faster than expected. As well as damaging concrete pillars and bridges, it has added to the problem of sand dunes that encroach upon the track.

Tunnels were built under elevated sections so that the endangered Tibetan antelope could pass by without danger. But planners have failed to cope with a far less timid and more numerous beast - the yak, thousands of which graze along the tracks and wander across them.

"These form dangers to passengers on the train," Mr Wang said.