SINGAPORE - Thirty-nine people were stranded mid-air after a mechanical fault halted operations at the Tiger Sky Tower ride in Sentosa on Saturday (Aug 12).

Those trapped, including tourists from Vietnam and four children, were rescued at 9.44pm, four hours after the fault was first reported at 5.35pm. The gondola, stuck 25m above ground, was lowered and all 39 of them emerged unhurt.

The cause of the mechanical fault is still being investigated. The Tiger Sky Tower will remain closed till further notice.

At 131m above sea level, the ride at Imbiah Road is the tallest observatory tower here, according to Sentosa's website. Introduced in 2004, the tower features an enclosed cabin with a capacity of 72 and revolves slowly to the top, offering passengers 360-degree panoramic views of Singapore and tourist island Sentosa's beaches and attractions.

At the time of the incident, 38 passengers and one ride operator were in the gondola, the Sentosa Development Corporation (SDC) said in a statement.

"On-site technical staff of Sky Tower immediately began troubleshooting the system. Bottles of water and food were also distributed to guests, as engineers from Sky Tower worked to lower the gondola. The capsule also has a mobile toilet," said the statement.

"Sentosa Rangers were subsequently called in to assist Sky Tower's engineers with the manual winching to lower the gondola," it added.

The Singapore Civil Defence Force (SCDF) said it was alerted to the incident at about 7.10pm. It dispatched a team, including members from its elite Disaster Assistance and Rescue Team (DART), as well as two fire engines, two Rescue Tenders and an ambulance to the scene.

It said in an earlier statement: "DART rescuers had ascended to the top of the tower before rappelling down to the immobilised passenger cabin, at about 25 metres above the ground. The cabin air-conditioning unit is functioning and there is provision of water for the trapped passengers in the cabin.

"The rescuers have checked on the trapped passengers and ascertained that all 38 passengers, including four children, are doing fine. The ride technicians are currently troubleshooting the problem and have managed to lower the cabin intermittently by a few metres."

When The Straits Times arrived at the scene at about 8.30pm, a crowd had gathered.

A woman, who wanted to be known only as Madam Lee, said she has five family members stranded in the gondola. She told The Straits Times that they have been stranded "for a long time". She added that she did not take the ride because she wanted to accompany her son who was not feeling well.

Just after 9pm, two hours after the rescue operation began, the gondola descended a few metres. Loud cheers could be heard from within the cabin. But, it soon came to a stop.

The Straits Times understands that a group of 15 Vietnamese tourists were among those trapped. They were part of a group of 21 who were here for two days, and were due to leave for Malaysia on Sunday.

The tour operator, who did not reveal the name of the company, said his main priority now was to make sure his clients were safely down. He said: "Right now, I just want to leave it to the experts here to assess and determine how to rescue the people in my group."

Law and Home Affairs Minister K. Shanmugam commended the SCDF for its rescue efforts.

He wrote in a Facebook post: "Singapore Civil Defence Force was involved in a few high profile incidents in the last 24 hours. Tonight, they helped 38 passengers and 1 operator trapped on Sentosa's Tiger Sky Tower ride."

The Sky Tower had also run into problems previously.

In July 2010, the tower had to be closed when it stalled with 10 tourists on board. The ride got stuck at the 55m mark during its descent, due to an uneven curvature on the track which affected the balance of the cabin.

Sentosa staff and Singapore Civil Defence Force personnel escorted the tourists, who were from Malaysia, down the emergency staircase. It took less than two hours for all tourists to be escorted down.

One month earlier in June, 36 passengers were left stranded 30m in the air for more than two hours when it stalled on its way down due to a mechanical fault. The ride was restarted after more than two hours after the SCDF and police were called in to help.