Two carriages of a new train that has been undergoing testing derailed at Bishan Depot yesterday.
SMRT spokesman Alina Boey said they "slipped off the track" while the train was pulling out of the stabling yard. No passengers were on board and there were no injuries.
The company stressed that the train had not been put into service yet and that normal services were not affected by the incident.
The Land Transport Authority (LTA) was informed of the incident at around noon.
A spokesman for LTA said some of the wheels on the third and fourth carriages were found to have been affected.
Neither SMRT nor the LTA elaborated on what caused the two carriages to go off the track, and it is unclear how the incident occurred.
SMRT staff were spotted along the tracks in the depot repairing the train yesterday afternoon.
They had separated the first two carriages of the six-carriage train to work on the third and fourth.
Said Ms Boey: "As part of SMRT's rigorous testing process for all new trains, we conduct comprehensive stress tests to ensure all train components are rail-worthy."
The spokesman for LTA said trains introduced into the MRT network are tested both overseas and locally before they are put into service.
She reiterated that the incident did not impact normal train operations and said the LTA will investigate the incident.