According to the announcement of MTR Corporation, a mechanical fault occurred when the involved train was preparing to enter the platform to Tseung Kwan O Station at around 8.57 am on Monday, causing the train to make an emergency stop.

The carriages involved, the sixth and the seventh, suddenly blackout during the incident.

About 1,500 passengers on board were directed by MTR staff to walk along the tunnel from the emergency exit of the train to the Tseung Kwan O Station platform.

This is the second incident in a month in which the passengers were forced to evacuate through the railway tunnel.

"According to a preliminary investigation, the incident was due to components in coupling connections between two carriages failing functions, which led to the train’s emergency brake equipment being launched," said Nelson Ng Wai-hung, chief of operations engineering, in a press briefing.

"The train was not derailed, and the service is now gradually resuming as our staff fixing the failed train," Ng added.

Services between Tiu Keng Leng Station and Po Lam Station / LOHAS Park Station are now disrupted, with trains travelling between Tiu Keng Leng Station and North Point Station keep five-minute intervals.

Free shuttle buses have been arranged at Tseung Kwan O Station for passengers.

The Electrical and Mechanical Services Department has requested the MTR Corporation to submit a preliminary investigation report within three days, and submit a detailed investigation report within two months.