Almost 27,000 morning rush-hour commuters were affected by the disruption of train services on all 16 Circle Line stations.
LTA said it has determined that the breakdown was due to a localised fault and that it was working closely with operator SMRT to ensure the Circle Line would open smoothly as planned.
Preliminary investigations have shown that a faulty cable located below the platform level of Dakota Station caused a power trip that affected the entire Circle Line system.
The disruption comes some two weeks before the final 12 stations of the Circle Line are opened for service.
The stations, running from Marymount to Harbourfront, will open on October 8.