Many questions remain about the tragic accident that left two new SMRT employees dead after they were struck by a train near Pasir Ris MRT station.

While the duo had just joined the public transport operator in January, SMRT Trains managing director Lee Ling Wee said they were trained and given a safety brief before they were allowed onto the track.

They were among a group of 15 staff walking in a single file along a 0.5m-wide walkway to investigate a possible fault 200m away from the station.

Facing the media for a brief session that lasted all of 13 minutes, SMRT chief executive Desmond Kuek said the walkway is safe for staff, and that a supervisor was in front of the two deceased.

How exactly the duo were hit by a train travelling towards the station on auto mode at about 60kmh remains unclear.

Mr Kuek could only say that the operator is still trying to establish from witnesses "exactly how they got on to the track or got close enough to the oncoming train".

He added that there was no closed-circuit television cameras along that stretch.

Accessing the track to investigate and fix faults is commonplace, said SMRT. And its operation control centre had given the staff permission to do so yesterday.

But there may still have been safety lapses. For one thing, should the train have been travelling in auto mode and at a speed of 60kmh with workers along the track?

The Straits Times understands that, as part of safety protocol, trains should be driven manually whenever there are staff working on the track.

A staff member stationed at the headwall of the station that the train is departing from - Tampines in this case - is also supposed to alert train drivers that there are men on the track, and to switch to manual.

Train drivers are meant to keep a lookout, and slow down when approaching a work party.

Was there a station staff member at Tampines who gave the alert, and did the driver know about the 15 men on the track?

If he did know, why was the train not driven in manual mode at a slower speed?

When asked if train drivers were aware of people on the track, Mr Kuek said this is among the facts SMRT is trying to establish.

In response to a query about whether trains should be in manual mode when staff are on the track and why it was on auto in this case, SMRT said these matters are also under investigation and that it could not comment further.

Many will be dismayed by yesterday's developments and might well wonder about the wisdom of allowing trains to hurtle past workers walking barely 0.5m away from the tracks, at 60kmh. The top speed of an MRT train is about 80kmh.

The speed of the passing train would be unsettling at the least, and lethal to any worker who, for whatever reason, falls onto the track or finds himself in its path.

At that speed, trains could not possibly stop in time.

The walkway that the 15 men were on has a width of about 0.5m, and is another about 0.5m away from the track.

There are no barriers, at least along the stretch of track near Pasir Ris MRT station, to act as a physical barrier separating the workers from trains.

Rightly, the operator is now reviewing all its safety protocols, and perhaps the design of such maintenance walkways is one of the things that need relooking.

In a note to staff after the two deaths yesterday, SMRT reminded them that "all safety procedures should be followed closely as they are there for our well-being and protection".

It is critical that it takes a hard look at its procedures and makes substantial improvements promptly, given that maintenance teams are sent onto the tracks while trains are running, several times each month to deal with faults.

As Prime Minister Lee Hsien Loong said in a Facebook post yesterday: "We understand that faults and malfunctions do happen in our train system, and generally take them in our stride. But it is different when two young men lose their lives in a workplace accident... Whether it turns out to be an unforeseeable mishap, an individual lapse or a system problem, we must do our best to ensure this does not happen again."

The deaths of the two young men were heartbreaking and seemingly avoidable. They also come on the back of an increase in the number of workplace deaths last year. According to statistics from the Workplace Safety and Health Institute, 66 workers were killed at their workplaces last year, up from 60 in 2014. At least 10 have died in such accidents in the first two months of this year.

Thankfully, no passengers on the train were seriously injured in the incident, and there were hardly any complaints about delays after word of the tragic deaths spread.

SMRT needs to get to the bottom of the incident, put things right, and inform the public just how it has done so, to assure all passengers and staff that they are safe.