A train fault near Hillview station affected services on the Downtown Line (DTL) and also dampened the mood of some attending an open house for a new stretch of Singapore's MRT network yesterday.

For at least 40 minutes from about 12.40pm, service was suspended between Bukit Panjang and Beauty World stations on DTL2. Service on DTL3, which will open this Saturday, was also affected.

On the way to the open house, which offered free rides and previews of the 16 new stations from Fort Canning to Expo, engineer Chu Ern Teng, 43, and his family waited 20 minutes at Bedok Reservoir station as the train heading to Fort Canning did not move.

"It is disappointing that this had to happen and it has spoilt our day a little and caused unhappiness. I do hope it will run smoothly once it opens," he said, referring to DTL3.

A train was stuck in a tunnel in the incident. A spokesman for SBS Transit, which operates the Downtown Line, explained last evening that while the system is driverless, all its trains are manned for contingencies such as breakdowns.

"Unfortunately, this train was to be manned from Hillview station but it developed a fault before reaching the station," said senior vice-president of corporate communications Tammy Tan.

Earlier yesterday, she apologised for the inconvenience caused.

A staff member managed to get on board the train, but took some time to get it moving. The incident led to no service between Beauty World and Bukit Panjang, and also in delays of about 20 minutes along the entire Downtown Line, which includes the DTL1 from Bugis to Chinatown.

SBS Transit announced the fault online at 1.04pm and free bus rides were made available at bus stops near affected stations. Service resumed at about 1.20pm after the train was taken off the line.

The opening of the 21km DTL3 will mark the completion of the Downtown Line, which spans 42km. It will become the longest underground and driverless MRT line, eclipsing the 35.7km Circle Line.

During the open house which drew close to 360,000 visitors, the Land Transport Authority hosted a bevy of activities at the new stations, with Senior Minister of State for Transport Lam Pin Min touring the stations. The Singapore Civil Defence Force held guided tours of civil defence shelters at various stations.

Housewife Vivian Chong, 42, who lives near the new Geylang Bahru station, said: "The noise and dust we endured for the past years are worth it as the station will bring a lot of convenience to us."

• Additional reporting by Christopher Tan