The power fault that caused service to be disrupted on the Downtown Line 1 on Friday night could have been triggered by a child who had accidentally activated the detrainment door device, said operator SBS Transit.

This caused the emergency brakes to be automatically applied, resulting in a tripping of the power supply to the line which is a safety feature of the system, it added. "Based on CCTV footage, we note that there were some children playing around the detrainment door area. A small girl appears to have accidentally activated the detrainment door device," said SBS Transit. "We are still investigating the incident and apologise to all affected."

Service on the newly-opened line was down at about 9pm on Friday, and resumed at 10.10pm. SBS Transit said 50 passengers on one train were detrained at Bayfront station. The operator deployed free bus bridging services for affected commuters, and buses passing by affected stations were also free.

It is the second breakdown for the six-station, 4.3km line which began operating just five days ago. The line runs from Chinatown to Bugis. On its opening day on Dec 22, service was disrupted for 15 minutes due to a train fault. The problem took place around noon at Bayfront station and delayed services between Bugis and Chinatown. It was quickly resolved and full service resumed not long after.