Commuters on the Downtown Line (DTL) had their journeys affected yesterday by a signalling fault that struck during evening peak hour and lasted more than 4½ hours.

Rail operator SBS Transit first announced the fault on its Twitter page at about 6.50pm.

It said then that commuters would face up to 15 minutes of additional travelling time between Expo and Geylang Bahru stations.

There are 10 other MRT stations located between Expo and Geylang Bahru.

In an update at 8.20pm, the operator said the extra travelling time would be about 20 minutes.

It also apologised for the inconvenience caused.

Several commuters complained about the fault on social media from about 6.30pm yesterday.

Some also disputed SBS Transit's claim of a 15-minute delay and said their trains were stuck at each affected station for about 10 minutes.

Similarly, a Straits Times reporter, who boarded the train at Mattar at 9pm to go to Bedok North, experienced a five-to 10-minute wait at each station before the train moved on.

A commuter, who wanted to be known only as Ms Gunawan, 32, said she had a 35-minute delay in her journey from Expo to MacPherson.

She added: "I took the Downtown Line because I had no other route home.

"I wish they would communicate (these issues) to the commuter more clearly.

"I had to check the Internet to know what exactly happened."

Temasek Polytechnic student Siamul Hoque, 17, who boarded at Bedok North, experienced a delay of about 25 minutes in his trip to Jalan Besar.

"To a small extent, I was frustrated but because I was with my friends, it was not that bad," he said.

Signalling systems are used to direct rail traffic and ensure a safe distance between trains.

Yesterday's DTL service disruption was the second major signalling fault along an MRT line this month.

On Dec 4, Thomson-East Coast Line services were disrupted for five hours because of a software glitch in the signalling system's network component.