“I apologise to all passengers who are affected,“ he said.

MTR did not reveal the total number of commuters affected by the incident.

Lu Wong Ho-leung, head of infrastructure works, said the cause of the damage remained unclear.

“From the preliminary inspection, a wire, which was part of the overline system, was found broken. But [as to] the real root cause, we [still] have to investigate,” he said.

He did not say how long the wire had been damaged and why MTR discovered the problem only on Friday morning.

Lu said the damaged wire triggered “the protection system”, which led MTR to suspend services.

Asked how regularly the company inspects its overline, he said MTR has its employees inspect the tracks and the overline system every three days. He added that MTR also runs test cars to gather data on the health of the track.

An earlier notice on the MTR website stated that the Airport Express had been fully suspended in both directions from Hong Kong Station to AsiaWorld-Expo Station, while services were down in both directions from Sunny Bay Station to Tung Chung Station on the Tung Chung Line.

Trains travelling between Hong Kong Station and Sunny Bay Station were running at 10-minute intervals, while those travelling between Hong Kong and Tsing Yi Station in both directions – some trains currently end their route at Tsing Yi Station – were arriving every five minutes.

Staff were earlier seen carrying out repair works. A weight, used to straighten the bent cables, was spotted at the site.

Free shuttle bus services, covering all Airport Express stations and between Sunny Bay Station and Tung Chung Station on the Tung Chung Line, were provided.

During the earlier disruption, more than 40 passengers were seen queuing for free shuttles to the airport at Hong Kong Station in Central.

One of them, a visitor from Macau who boarded the bus at 10.20am, said she was likely to miss her flight to Shanghai at 11am.

Another passenger, Sinni Kurt, a visitor from Melbourne, Australia, said he had a “50-50” chance to catch his 1.10pm flight to Melbourne.

Those who were headed toward the AsiaWorld-Expo were also affected. Christoph Rowen from Hong Kong said he was unaware of the service disruption when he first got to the station.

“But at least they have buses to pick us up. [The temporary arrangement] is very organised. It’s very efficient” he said.

Passengers on a shuttle from Kowloon Station to the airport and AsiaWorld-Expo agreed that the train service disruption was an inconvenience, although they praised the shuttle bus arrangement.

James, a commuter who was on his way to the Expo for the Global Sources electronics show, said the delay was a “major problem” and believed he would not be able to make his noon appointment.

Tourists Dominic and Kirsty were on their way to the airport to catch a flight to Japan.

“We were really worried when we saw the sign that we were going to have to make alternate arrangements,” Dominic said.

But he heaped praise on the MTR staff for being “thoroughly organised” in providing the shuttle bus.

Since the Airport Express and Tung Chung Line opened in 1998, they have been plagued by a series of disruptions, including a four-hour interruption to both lines in June 2001 that affected thousands of passengers.

The delays were caused by damage to overhead lines, which interrupted power supply at the Siu Ho Wan depot near Hong Kong International Airport in Chek Lap Kok.

In July, a signalling fault, also at the Siu Ho Wan depot, caused delays on the Airport Express and Tung Chung Line for about half an hour.