A track fault on the East-West MRT Line yesterday caused the most serious rail disruption since January.
The fault near Paya Lebar station, suspected to have been triggered by a works vehicle during the pre-dawn maintenance shift, lengthened travelling time by up to 30 minutes on the westbound track during the morning rush hours.
Service was affected for nearly four hours, with normal service resuming only by 10.10am.
Commuters tweeted about the train disruption from as early as 6.30am.
Finance analyst Kat Lee, 30, said her trip from Bedok to Paya Lebar took more than 25 minutes.
"Normally the train ride for the same distance takes slightly more than five minutes," she said.
"The delay caused me to be 15 minutes late for a meeting I was hosting."
Yesterday, SMRT had initially announced that journey times would take 15 minutes longer. It then progressively revised this to 20, 25 and finally, 30 minutes.
The disruption affected thousands of commuters travelling during the morning commuting hours from 6.30am to around 9am.
Checks carried out by The Straits Times found that neither trains nor stations between Aljunied and Raffles Place were packed from 9.30am.
By around 9.40am, station announcements stated that the track fault had been rectified, but service was not up to speed yet because of congestion. Normal service resumed only by 10.10am.
SMRT spokesman Patrick Nathan said the disruption was traced to a faulty track signal circuit.
"Our engineering staff replaced the faulty track circuit while some trains were halted momentarily for the repair work," he said.
"Initial investigations revealed that overnight track work by a track tamping vehicle, which is used to compact the ballast that supports the tracks, may have damaged the track circuit."
He added: "We are sorry for the inconvenience caused. Procedures will be strengthened for overnight track work to prevent a recurrence of the incident."
The last major breakdown affecting a long stretch of the MRT took place on Jan 28, when a train fault disrupted morning rush-hour commute on the East-West Line.
During that disruption, travelling time from Aljunied station to Jurong East station took 25 minutes longer. Service resumed fully about an hour later.