The Qinghai-Tibet railway, opened last month to great fanfare, is developing surface cracks in its concrete structures while its permafrost foundation is sinking and cracking in some sections.

"The frozen ground that forms the foundation of the railway is sinking and cracking in some sections, making the railway unstable in some places," the Beijing News quoted railway ministry spokesman Wang Yongping as saying.

"The concrete is cracking on some of the railway structures and bridges, forming a hidden danger to the railway line quality."

Wang said experts are working on these problems and relevant authorities have taken measures to ensure the safety of the rail and passengers, without specifying these measures.

The railway to Lhasa, capital of Tibet Autonomous Region, was opened on July 1. It was hailed as a magnificent engineering feat and a miracle for the world.

The US$4.2-billion railway, which runs 1,142-kilometers from the desert outpost of Golmud in Qinghai province to Lhasa, is the highest in the world.

It climbs a peak 5,072 meters above sea level along the Tibetan plateau, with the railway using supposedly state-of-the-art cooling techniques to ensure the permafrost foundation remains frozen.

Editor: Donald