SINGAPORE - The Transport Ministry will not call for a public inquiry into the unprecedented flooding of MRT tunnels which paralysed a large part of the North-South Line for about 20 hours on Oct 7 and 8.

Transport Minister Khaw Boon Wan told Parliament Tuesday (Nov 7) that the cause of the incident was clear cut, and was attributable to nothing else but maintenance lapses.

"While investigations by LTA (Land Transport Authority) will take a few more weeks to complete, the facts of the Oct 7 incident are not complicated, and the cause of the incident is clear," Mr Khaw said in response to a question filed by Mr Zaqy Mohamad (Chua Chu Kang GRC).

"My Ministry will therefore not be convening a Committee of Inquiry," he added.

Mr Khaw said the tunnel flooding was preventable: "It should not have happened."

"It was not due to any inadequacy in the design of flood prevention measures. Neither was it due to an extraordinary storm. It was due to poor maintenance and neglect of duties by the specific SMRT maintenance team responsible for the Bishan storm water sump pump system," he said.

The minister noted that all the three pumps in the Bishan sump pit were working, and all five float switches in the system were also functional.

"Why these float switches failed to function normally on Oct 7 is a subject of the ongoing LTA investigation," he added.

SMRT had found that the team of six staff responsible for the Bishan flood prevention system may have falsified records on three occasions, meaning the pumps were not maintained for at least nine months.

Although the team submitted maintenance records, SMRT found that track access was not granted on those dates and the pumps were not activated.