The East-West MRT line suffered its third breakdown in a week yesterday morning.
An eastbound train leaving Jurong East station developed a signal fault at about 6.50am, said SMRT spokesman Patrick Nathan.
"The train captain was able to recover (momentarily overcome) the fault, and the train was turned back to Jurong East station where passengers were detrained before the train was pulled out of service," he added.
SMRT made announcements at affected stations and on board trains, but did not post a Twitter alert.
Commuters tweeted that the breakdown lasted as long as 40 minutes, with some saying they were stuck onboard for 20 to 25 minutes.
Sales assistant Jackson Teo, 20, said the Clementi-bound train he was on had been travelling slowly before it was announced that it could not continue.
"The train stopped between Clementi and Jurong East stations for a while before it moved back to Jurong East station," Mr Teo told The Straits Times.
"We were then told to alight and wait for the next train."
Last Tuesday, a track fault caused train delays of up to 20 minutes between Tanah Merah and Bugis stations.
Three days later, a westbound train near Dover station had its brakes stuck during the morning rush hour, leading to longer travelling times for thousands of commuters.
SMRT's Mr Nathan could not explain the spate of incidents beyond saying the three were unrelated.