On 7 October 2017, water got into a section of the tunnel between Bishan and Braddell MRT stations during a heavy downpour in the afternoon, which disrupted train services along 13 stations on the North South line for several hours. This case of water entering MRT tunnels is believed to be the first time it has affected train service along the NSL. Separately, at about 5.55pm, a small fire was spotted trackside in the tunnel between the Marina Bay and Raffles Place stations, but it had died down by itself. It is not clear if it is linked to the flood, although electrical short circuits caused by water had sparked tunnel fires before. Train services between Marina South Pier and Newton were restored on the day itself at about 9.20pm. Train services between Newton and Ang Mo Kio were fully resumed at 1.36pm the following day after overnight efforts to clear the water in the tunnel, after nearly 21 hours of service disruption, being one of the worst disruptions in SMRT Trains Ltd's history. It was revealed that the overflowing in the tunnel was caused by a malfunction in the water pumping system, which has since been repaired.
