SINGAPORE - Emergency brakes applied for an unknown reason are understood to have rendered a Circle Line train inoperable near Marymount station during the morning peak period on Monday (Sept 11).

The faulty train had to be pushed out by another train.

The episode - just two days after a track fault disrupted service on the Bukit Panjang LRT for some six hours on Saturday morning - affected thousands of commuters on their way to work and school.

According to the Singapore Examinations and Assessment Board, a number of N-level exams were held on Monday morning.

Circle Line operator SMRT first tweeted about the fault at 9.25am, warning of journeys taking 15 minutes longer. Later, it revised this to 30 minutes.

But National University of Singapore student J. R. Tan's journey from Bartley station to NUS took nearly an hour longer. After getting stuck in a train that was crawling and stopping, the second-year student got off at Botanic Gardens station and took a bus.

The 22-year-old said she missed two-thirds of a lecture. "When the train stalled at Caldecott, they announced that it was going to be a five-minute delay. Then 30 minutes later, they said it was going to be a 30-minute delay.

"If they had said 30 minutes from the start, I would have gotten off and taken the bus, and maybe made it in time for my lecture."

Across the network, crowds packed station platforms.

Past 10am, SMRT tweeted to say service was recovering gradually.

It was not the first time a train service was affected by emergency braking. Usually, a train will apply emergency braking if it senses a safety breach.

Almost exactly a year ago, the Circle Line was beset with cases of trains applying emergency braking intermittently. The long-drawn saga was initially attributed to an unidentified signal interference, and the Land Transport Authority even considered equipping the trains with an "electromagnetic shield".

The fault was finally traced to a faulty train which was emitting rogue signals which affected other trains.