SINGAPORE - SMRT will be taking disciplinary action against six of its staff who were part of the team assigned to carry out maintenance work on the Bishan water discharge system, which malfunctioned and led to a 20-hour service disruption last month.

Another seven managers from the same maintenance group, including two executives who hold vice-president positions, will also be investigated. All of them have since been suspended "with respect to their discharge of supervisory responsibility", said the rail operator in a statement on Monday (Nov 6).

It added: "As part of our value system of shared responsibility and accountability, the company will also take this incident into account when reviewing the remuneration of its senior management, from the CEO through the relevant chain of command."

The move comes as SMRT wrapped up its investigations into the maintenance of the Bishan pump system. It was prompted by the flooding of an MRT tunnel last month that brought down train services on a stretch of the North-South Line for about 20 hours. The float switches that were designed to pump water out of the pit at Bishan station were suspected to be faulty before the downpour.

What it found was that maintenance records by the six-member team had been falsified between December last year and June this year. The team that is under fire falls under the building and facilities maintenance group, and comprises a manager, an engineering supervisor and four other crew members, it said.

SMRT also noted that it is currently studying "a number of submissions" it had received relating to the scheduled maintenance works not being carried out - also from the building and facilities maintenance group - following an offer of amnesty to report maintenance lapses, which ended last Friday (Nov 3).

During the amnesty period, staff who owned up to not having done work, or not adhering to company procedures or instructions would not be penalised. The move is aimed at quickly plugging gaps in the system.

Meanwhile, other maintenance units - such as rolling stock, signalling and communications, permanent way and power maintenance - have been assessed and found to be compliant with specified maintenance standards, said SMRT.

The National Transport Workers' Union (NTWU) executive secretary Melvin Yong called on SMRT to share information on its investigations with the NTWU, and include the union in its disciplinary inquiry.

Mr Yong added that the union hopes SMRT will take a "balanced approach" in both its investigations and disciplinary inquiry.

"We also urge SMRT to define clearly and communicate what amnesty means and how it would be administered fairly to allay workers' concerns on the ground and ensure that workers would not suffer undue stress by the process," he said.

SMRT said it is also cooperating with the Land Transport Authority's investigations into the flooding incident on Oct 7, which are ongoing.

The rail operator added the newly formed Joint Readiness Inspection team - announced last Tuesday - will step up on "enforcement of ground practices and standards", assisting its existing internal audit and inspectorate teams.

In a written response to a parliamentary question by Non-Constituency MP Leon Perera - who asked whether the Oct 7 incident would affect the pay of staff from the Ministry of Transport (MOT) and the LTA tasked with overseeing the MRT, Transport Minister Khaw Boon Wan said there was no evidence of "shortcomings or lapses in regulatory oversight" by either LTA or MOT.

He said the responsibility for maintaining rail lines - including flood prevention systems - lies with operators, adding that on Sept 29 the LTA had requested from SMRT a list of pumps requiring replacement, as well as the need to maintain tunnel pump systems.