A train on the Bukit Panjang LRT (BPLRT) that failed to stop at three stations last Thursday had a fault in its antenna, which ensures the fully-automated train stops accurately at each station, operator SMRT said.

In a statement yesterday, it said the faulty antenna prevented the train from picking up the signal to stop at Jelapang, Senja and Bukit Panjang stations.

SMRT was responding to a Facebook post by housewife Jacqueline Bong, detailing her experience on the train, which she described to The Straits Times as "alarming" and "scary".

After completing a yoga session, the 40-year-old boarded a train at nearby Segar station with a friend at about 11.45am.

She was going only one stop, a distance which she usually covers by walking, except that it was raining heavily.

"When the train did not stop at Jelapang, we tried pressing the emergency button, but it was not working," she said.

"A man in my carriage picked up the emergency phone and tried calling, but there was no response.

"The train was going quite fast and it did not slow down as it usually does at corners."

She said the two-carriage train, which had about 20 passengers, finally came to a stop outside the platform at Phoenix, four stations down the line, after another commuter rang a number listed in the train on her mobile phone.

An SMRT staff member subsequently arrived, forced open the door and drove the train to the platform where everyone got out, she added.

Ms Bong, who lives in Choa Chu Kang, said she takes the BPLRT every day and this was the first time something like this had happened.

In her Facebook post, she asked why the train's emergency button and phone did not work.

SMRT said the train's emergency halt request button can be activated only when a train comes to a complete stop at a station and prevents it from moving off again.

The BPLRT Operations Control Centre (OCC) had also received separate alerts from commuters through the station intercom, the train's emergency phone and the OCC hotline, it added.

SMRT said the control centre then imposed a "speed code restriction", which stopped the train before Phoenix station.

Though Ms Bong had thought the train was moving quite fast, SMRT said it did not exceed 55kmh during the incident.

BPLRT trains typically operate at between 30kmh and 55kmh.

"The train was later withdrawn to the depot for further checks. All equipment in the train, including the emergency phone, is checked before the train is put into service each day," it said in its statement.