SINGAPORE - Commuters on an east-bound train were forced to alight at Tanjong Pagar MRT station on Thursday morning (June 7), after white smoke engulfed the platform due to a freon gas leak.

In response to queries, transport operator SMRT, which runs the East West Line, said that staff had detected the smoke from beneath the train while it was stationary at Tanjong Pagar MRT station at about 9.45am.

SMRT's preliminary investigations show that the leak was due to a leaking air-conditioning compressor that released freon gas.

Freon gas - a common refrigerant used in air-conditioners - is non-toxic, but interacts with moisture in the air to form an odourless white smoke.

However, prolonged exposure to the gas, especially when it is deeply inhaled, can cut off oxygen to the cells and lungs.

"As a safety precaution, all passengers on board the affected train were asked to alight and board the next train," said Ms Margaret Teo, vice-president of corporate communications.

She added that the affected train was withdrawn from service for further checks.

Account manager Roland Yeo told The Straits Times that the platform was "quite smoky", and the source of the smoke appeared to be from the rear of the train he was riding.

The 41-year-old, who was heading to work at Raffles Place, said that the smell had not been obvious from where he was, in the middle of the train.

He only noticed the smoke after the train pulled into Tanjong Pagar MRT station and he was asked to alight.

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"After the train stopped, the staff told us to alight quickly without really explaining what had happened," he said.

"There were also no announcements made, but people started to notice the smoke, so everyone cooperated with the staff."

He said it was calm and orderly at the station, adding that commuters did not face much of a delay as they could board the next train that arrived about two minutes later.

Most recently in March, a train was withdrawn from service after a freon gas leak at Jurong East station.

In October 2017, Transport Minister Khaw Boon Wan said in a written Parliament reply that there have been 23 instances of such leaks on trains over the past decade.

In May 2017, a freon gas leak on a train caused smoke to engulf the Raffles Place station platform.

And in August 2016, a similar incident occurred at Tanjong Pagar MRT station, initially sparking fears of a fire.

SMRT later said that the train's air-conditioning compressor had become overheated after oil leaked, resulting in a release of freon gas into the platform area.