The system automatically shut down and service resumed at 4.30pm. Previous delays during the period after the system was brought back into service in December were no longer than eight minutes.

Broadcasts inside the gondola informed passengers about the problem three minutes after the system halted, although some passengers complained they were not informed.

Ngong Ping 360 cable car officials were investigating last night, but a spokesman said it was a one-off incident and normal service would resume today.

The former president of the Hong Kong Institute of Engineers, Edmund Leung Kwong-ho, said the error was an operational one without safety implications. 'Even if the belt slipped away from the pulley, the gondola would not fall, because it is not the belt but a rail track inside the terminal that supports the weight of the gondola,' Mr Leung said.

He said a set of conveyor belts at the terminal building replaced the cable system that propelled the gondolas when they arrived at the terminal. Those conveyor belts were propelled by a set of tyres. If a tyre shrank because of air leakage or any other reason, it was possible for a belt to move out of position.

'I would not suspect negligence on the part of maintenance workers,' he said. 'First, a flat tyre happens all the time for all kinds of reasons. Second, it is just normal that more attention would be given to safety devices such as sensors, pegs and grips instead during regular inspection.'

Mechanical engineer Lo Kok-keung agreed, adding that the MTR Corp had been quick to spot and fix the problem.

The last inspection was conducted on February 6 and the next one is scheduled on April 8 and 9.

The Electrical and Mechanical Services Department, whose staff investigated the scene, has asked for an incident report.