The Bukit Panjang LRT line was out of action for almost five hours yesterday after a train damaged a signal stop tape near Keat Hong station.

A signal stop tape is a piece of trackside equipment which determines precisely where and when a train stops at a station.

It is not immediately known how the train was able to hit the tape, which is always sited well away from the path of travel.

The incident, which occurred at 1.45pm, disrupted service on the entire line as workers withdrew the damaged train for inspection, replaced the damaged equipment and checked the network for other damage.

Service resumed at 6.30pm.

Replacement buses, as well as regular bus services, allowed passengers on for free while train services were down.

In its first tweet at around 2.30pm, operator SMRT said there was no service on the line because of a track fault, adding that free replacement bus services were available at the 14 affected stations.

At around 3.50pm, it put out an update, saying that a train had damaged a signal stop tape near Keat Hong station at 1.45pm.

SMRT said the damaged train had been withdrawn from service for further checks, and that its engineering team was conducting a systemwide safety check to determine whether other parts of the system had also been damaged.

"Our engineering staff are now working to resume service," the operator added then. "We are sorry for the inconvenience this has caused to BPLRT commuters."

At 6.05pm, SMRT tweeted that service had resumed partially between Bukit Panjang and Senja.

The Straits Times understands that the replacement buses arrived in intervals of eight to 10 minutes, depending on traffic conditions.

Mr Mason Teo, 38, a Bukit Panjang resident, was on his way home at around 3.50pm when he was stopped by customer service staff at Bukit Panjang LRT station.

"I am figuring out how to go home now. I have no choice but to take a bus," the interior designer said. He added that he frequently gets caught in MRT and LRT breakdowns.

"But I have never been in one that has affected the whole line before," he said. "My house is just five stations from here. So near, yet so far."

Zhenghua Secondary 2 students Fion Chua and Trixie Ng, both 14, had planned to take the LRT to school, from Bukit Panjang to Jelapang station, to attend a camp.

But they did not know which bridging bus service would take them to their school.

"We might as well walk to school at this rate," said Fion.

Their schoolmate Glenys Wong, 15, managed to find the bus service that would take her home, but said: "It is quite a tedious process.

"I am not in a rush, but I think those who are would be very inconvenienced. Compared with the LRT, this is really not the fastest way to go home."

But full-time national serviceman Jo Tham, 21, who also had to shelve plans to take the LRT home, said there was "no point complaining about the breakdowns". "They are upgrading the system, so it is better for us in the long run," he said.

The 18-year-old Bukit Panjang LRT has been saddled with reliability issues, partly because it has to contend with undulating terrain and sharp turns.

It is Singapore's third-oldest line after the North-South and East-West MRT lines.

Transport Minister Khaw Boon Wan said last year that the system was built as an "after-thought" and due to "political pressure".

Mr Khaw also said the 7.8km line was designed in a "masochistic manner", and likened the ride to a "roller coaster".

The Land Transport Authority said last month that it would be awarding a contract early this year for the replacement and renewal of major components and systems of the Bukit Panjang LRT.

On Sept 9 last year, broken rail support brackets on the Bukit Panjang LRT resulted in train services on the entire line being unavailable for about five hours.