The mishap disrupted services during morning rush hours between Tiu Keng Leng and Po Lam stations, and between Tiu Keng Leng and Lohas Park stations for about four hours, and forced 1,500 passengers to walk through the tunnel to the Tseung Kwan O station.

The MTR Corp said in an initial report earlier that the energy absorption device of the coupler was dislodged. which resulted in the gangway between the sixth and seventh cars being lengthened, activating the train's fail-safe mechanism and bringing the South Korean-made "K-train" to a stop.

Speaking at a Legco meeting today, an MTR spokesman said the device’s design is unique and the inspections could only be carried out by shipping it to its manufacturer.

It noted there have been guidelines requiring the devices to be checked once every nine years, with the device last inspected four years ago in 2018.

The spokesman said the MTRC will conduct a review on its existing asset management and maintenance regime, adding that the corporation has invested up to HK$10 billion in its asset management in recent years.

Speaking at the same meeting, Deputy Secretary for Transport and Logistics Amy Wong Pui-man said the SAR government has since requested the MTRC to submit a detailed report about the incident in two months.

She said the railway operator is required to conduct an in-depth investigation to confirm the cause of the incident and review the handling of the incident, and put forward improvement measures.

An independent commission was also set up by the SAR government to oversee the railway operator’s review efforts, she added.