SMRT forked out about $2 million on repairs and replacements to rail equipment after a flooding incident last October near Bishan MRT station, Transport Minister Khaw Boon Wan said yesterday.

The flooding had submerged trackside equipment and components installed on the undercarriage of a train that stalled in the tunnel between Bishan and Braddell stations, Mr Khaw told Workers' Party Non-Constituency MP Leon Perera in a written reply.

"The cost of repairs and replacements amounted to about $2 million. This was borne by SMRT," he said.

The unprecedented flooding on Oct 7 had disrupted services along a section of the North-South Line for about 20 hours, and affected 250,000 commuters.

Flood waters were up to 1m deep and spanned 100m of tracks in both directions.

It took an overnight effort involving teams from the Singapore Civil Defence Force, PUB, the Land Transport Authority (LTA) and SMRT to pump out the water.

In an investigation report released last year, the LTA said the incident was entirely preventable.

It noted that flood prevention measures were more than adequate and had a huge buffer, but a lack of maintenance, audits and managerial supervision led to the water pit being likely close to full when the downpour happened that day, making flooding inevitable.

SMRT later found that its staff had falsified maintenance records over a seven-month period, signing off on work that was not done.

In the aftermath, the rail operator took disciplinary action against the staff involved, including sacking eight employees and demoting one.