An SMRT worker had his right foot amputated yesterday after it was crushed in an accident involving a maintenance vehicle on the MRT tracks near Joo Koon station.

How the accident happened is unknown, but The Straits Times understands that the employee - a man in his late 50s - was injured by a track tamping vehicle, which is used to compact the ballast that supports the tracks.

The accident occurred at about 4.10am near Joo Koon, said SMRT yesterday. It delayed the start of train service on the East-West Line in both directions between the Gul Circle and Boon Lay stations by about an hour, till 6.20am.

The worker was conscious when taken to the National University Hospital in an ambulance, said the Singapore Civil Defence Force.

"Our staff's right foot was injured as he was on track preparing for an engineering vehicle to move back to the depot after completion of maintenance works this morning," said SMRT corporate communications vice-president Margaret Teo yesterday.

The man's two sons, who declined to be named, told The Straits Times their father is in a stable condition after an operation in the morning. He is warded in the hospital's intensive care unit.

They said their father could chat normally to family members and colleagues, but was still in a state of shock. The man is married with three adult children.

SMRT said it will carry out a full investigation into the accident, and added that its maintenance teams observed a safety time out yesterday morning. The rail operator is providing the necessary care and support to its employee and his family, Ms Teo said.

FINDING OUT WHAT HAPPENED We will be working closely with the company to investigate the cause of the incident, and to review the necessary workplace safety measures. MR MELVIN YONG, National Transport Workers' Union executive secretary, in a Facebook post.

When asked for details on how the accident occurred, SMRT declined to comment and would only say that investigations were ongoing.

Yesterday's accident is the most serious of its kind since two SMRT trainees were killed by an oncoming train near Pasir Ris station in March 2016.

Mr Nasrulhudin Najumudin, 26, and Mr Muhammad Asyraf Ahmad Buhari, 24, were on the tracks investigating a possible fault when they were killed by the train.

Investigations later found that safety protocols which would have prevented their deaths were not in place, and SMRT was fined a record $400,000 for the incident.

Yesterday, SMRT said its engineering and operations teams conducted further checks on the tracks after the injured worker was taken to hospital, before service between Gul Circle and Boon Lay started at 6.20am.

Related Story SMRT employee injured during maintenance work at Joo Koon MRT station, leading to delay in EWL train service

The westbound train service from Boon Lay to Gul Circle typically begins at 5.21am on weekdays, while the eastbound service from Gul Circle begins at 5.26am.

Free regular and bus bridging services were activated between the four-station stretch as an alternative for affected commuters yesterday morning, SMRT said.

In a Facebook post, National Transport Workers' Union executive secretary Melvin Yong said the union will be assisting the injured worker and his family. "We will be working closely with the company to investigate the cause of the incident, and to review the necessary workplace safety measures," said the Tanjong Pagar GRC MP.