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", the rail operator said in a statement yesterday.
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 on Oct 7 that disrupted 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 the rail operator found was that maintenance records by the six-member team had been falsified between December last year and June this year.
The team from the building and facilities maintenance group comprises a manager, an engineering supervisor and four other crew members, SMRT said.
It also said it is currently studying "a number of submissions" it had received relating to 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.
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 have been assessed and found to be compliant with specified maintenance standards, said SMRT.
National Transport Workers' Union executive secretary Melvin Yong called on SMRT to share information on its investigations with the union, and include it in its disciplinary inquiry.
Mr Yong added that the union hopes SMRT will take a "balanced approach" in both its investigations and disciplinary inquiry. He urged the company to define the terms of its amnesty deal and explain how it will be administered fairly.
SMRT said it is also cooperating with the Land Transport Authority's (LTA) investigations into the flooding incident, which are ongoing.
Separately, in a written response to a parliamentary question by Non-Constituency MP Leon Perera, Transport Minister Khaw Boon Wan said there was "no evidence of shortcomings or lapses in regulatory oversight" by either LTA or the Transport Ministry with regard to the flooding incident.
Mr Perera had asked whether the incident would affect the pay of ministry and LTA staff tasked with overseeing the MRT.
Today, Mr Khaw will deliver a ministerial statement in Parliament addressing questions from 10 MPs, from both the People's Action Party and the Workers' Party, on what caused the flooding, and how it can be prevented in the future.