On March 20, a photo of a MRT train with smoke coming from it surfaced on Reddit.

This is the photo, which appears to be taken at Buona Vista MRT station:

Apparently, the incident took place on Wednesday, March 20, 2019.

Due to air-con refrigerant leak

It has since been confirmed that the incident did happen.

A statement released on SMRT's Facebook page late on March 20 night at 11:24pm confirmed the incident at Buona Vista MRT station.

The train was bound for Pasir Ris at that time.

The incident occurred around 7:45am.

As a safety precaution, all commuters were asked to alight and take the next train. The train was also withdrawn for further checks.

In the post, it was explained that the smoke emission was "due to an air-conditioner refrigerant leak".

This is their post and statement in full:

Some of you may have heard about an incident at Buona Vista station this morning. Here is what happened.

This morning (20 Mar) at around 7.45am, white smoke was seen coming from a train at Buona Vista MRT Station along the East-West Line towards Pasir Ris. As a safety precaution, all commuters onboard the train were asked to alight and take the next train. The train was immediately withdrawn for further checks. We have confirmed that the smoke emission was due to an air-conditioner refrigerant leak.

Top photo via via Reddit u/snowfox_my