The track under the world's first commercial magnetic-levitation train is sinking, possibly threatening the £700m project, the newspaper Shanghai Daily reported yesterday.

The 270mph "maglev" began regular operation this year. It links Shanghai's new international airport with its financial district.

Officials in Shanghai would not comment on the report. But Xia Guozhong, a spokesman for Shanghai Maglev Transport Development Company, which runs the project, was quoted as saying: "We have been aware of the sinking of our maglev track."

A spokeswoman for Shanghai's municipal government said she had no information, but that her office was checking the newspaper report.

Calls to the government's department of major projects were unanswered.

German companies spent decades and billions of dollars developing maglev technology, but searched in vain for a customer until Shanghai leaders chose the system to highlight the city's hi-tech ambitions.

While some settling was normal, too much could harm the project, Shanghai Daily quoted Chinese experts as saying. "If the track sinks beyond its safety level, managers will have to stop the line's operation," Yu Jiakang, a senior engineer with the Shanghai Tunnel Engineering and Rail Transit Design and Research Institute, said.

Speaking to Associated Press, Mr Yu said track settling could be arrested by reinforcing subsoil.

"Slight sinking isn't a problem," he said. "It should be possible to reinforce subsoil for the maglev if necessary."

Shanghai is built on swampy land and has long faced problems with subsidence.

Officials called for stricter building codes after the collapse last year of an eight-storey building was blamed on the excavation of a nearby pedestrian tunnel. No one was injured in the collapse.

Sinking tracks are not the only problem facing the maglev, which uses a powerful magnetic field to lift trains millimetres above the rails and propel them at the speed of a jet plane.

The 440-seat trains carried an average of just 73 passengers a day last month, the Shanghai Daily said. At 75 yuan (£5) each way, tickets are considered too pricey for most residents.

The train's station is also inconveniently located outside of the centre of town.

It was hoped the maglev would be used on other, long-distance, lines in China. But the government has ruled it out for a planned high-speed line linking Beijing and Shanghai.

There has been no decision on a proposal to use the maglev on a line between Shanghai and the nearby city of Hangzhou.