Commuters travelling between Ang Mo Kio and Marina Bay on south-bound trains were delayed by 20 minutes on Tuesday night after yet another track fault.
The latest hold-up on the North-South line comes just a day after a track circuit failure on the same line caused a 50-minute delay during Monday morning rush hours.
At 10.23pm on Tuesday, SMRT issued a tweet to say that the problem has been fixed and the service from Ang Mo Kio towards Marina Bay was operating normally.
Since the new year, commuters have had to put up with a spate of delays on MRT trains. There have been four incidents on the North-South and East-West lines that resulted in delays of more than 30 minutes. This is already half the number of such train delays in total for the whole of last year.
The Land Transport Authority had earlier said that it would look into Monday's incident, which comes a week after heftier penalties against serious train disruptions were legislated. Under new laws, operators can be fined up to 10 per cent of the annual fare revenue of an affected line, or $1 million, whichever is heftier.
The previous cap was at $1 million per incident.