A corroded metal strip caused a rail crack between the Yio Chu Kang and Ang Mo Kio stations that delayed the peak-hour crowd on Thursday morning, said SMRT on Friday.
This cause the underside of the rail to weaken and eventually crack. SMRT's spokesman added that the galvanic corrosion happens over time and that in this instance, routine ultrasonic and multi-functional vehicle (MFV) tests were not able to detect this defect because it was on the underside of the rail.
She added: "It could happen again, as it is symptomatic of aging rail infrastructure." This crack which is the third in five weeks, is different in nature from the previous two which were on the welded portion of the rail.
"A discussion on an entire systems overhaul is being tabled with the Land Transport Authority. This overhaul is seen as absolutely necessary for system safety and reliability moving forward," she added.