The four-month-old Downtown Line 2 had its first major breakdown yesterday morning when a train inexplicably applied its emergency brakes.
The fault happened at 11am and took around half an hour to resolve.
Operator SBS Transit said at 6pm that it was still investigating why the emergency brakes were applied and why they could not be disengaged.
The affected train, which held up services between Bukit Panjang and Sixth Avenue stations, was eventually removed. The disruption caused SBS Transit to deploy buses to ferry affected commuters.
Meanwhile, operator SMRT reported a train fault at Toa Payoh station along the North-South Line at 5.45pm, which delayed northbound service towards Jurong East.
It told commuters via its Twitter feed to expect additional travelling time of 25 minutes from Marina South Pier to Toa Payoh. At about 6.15pm, it said service had resumed but added that trains may be moving more slowly due to the fault.