SINGAPORE - Commuters along the North-South Line were told to add 20 minutes of travel time between Marina South Pier and Jurong East on the North-South Line during the evening peak hour on Thursday (June 1).

Photos sent to The Straits Times show long queues at Raffles Place and Newton stations.

On social media, others wrote about facing delays as well, at stations including Jurong East, Ang Mo Kio, Yio Chu Kang, Bukit Batok and several others.

IT executive Kelvin Ong told ST that he had been on the train from Kallang at 6.10pm when he saw a huge crowd at City Hall.

He decided to switch to the red line at Raffles Place but "it was even worse".

Mr Ong, who usually takes about 40 to 45 minutes to get home to Woodlands, was at Bukit Batok station when he spoke to ST at 7.20pm.

He said the situation was "chaotic", and some people waited for 45 minutes for a train at Jurong East station.

"It's really very, very bad because directions are not clear and most of us are not given clear instructions," he said. "I'm not sure what they are testing. At this hour it's not really convenient."

Mr Ong, who is in his late 30s, said the platform at Jurong East was packed with people and they were asked to disperse.

"I just pray I can reach home faster," he said.

PR executive Sarah Chua, 28, told The Straits Times that she was heading home at about 6.45pm when she saw "an unusually big crowd" at City Hall MRT Station.

Ms Chua, who lives at Simei, then switched to the Circle Line instead. She said while it will take longer to get home, she hoped the crowd would ease by the time she got to Paya Lebar.

SMRT said in a tweet at 6.47pm: "Due to new signalling system checks, pls add 20mins travel time between #MarinaSouthPier & #JurongEast both bounds. We are sorry."

It later said free regular bus services were available at certain stretches on the train line.

At 7.17pm SMRT said trains were progressively returning to normal speed and asked commuters to expect 15 minutes' additional travel time between Marina South Pier and Jurong East.

It also asked commuters to remain calm and follow in-train announcements.

Keith Chong, a 23-year-old student, told ST that he decided to take a bus instead after seeing the large crowd at Bishan at 6.50pm.

He said there were announcements made about the delay and "a lot of staff guiding people".

Another commuter, 32-year-old Eugene Mok, said: "The trip from Yew Tee (6:20pm) to Bukit Batok (7:08pm) took 48 minutes. A typical 8-min trip for 3 stations took an extra 40 minutes."

SMRT said in a tweet at 7.41pm that train services were returning to normal.

The line was also reportedly plagued by delays throughout the day.

Housewife Madeline Tan, 56, said the train stopped for up to five minutes at each station in the afternoon when she took the train from Orchard to Novena at around 1.30pm.

"My chicken was defrosting on my lap," she said.

Testing on the upgraded signalling system began in late March. The Land Transport Authority and SMRT had previously said that the new system will allow trains to run at shorter intervals of up to 100 seconds, instead of 120 seconds during peak hours.

It was also unveiled as one of the key projects to renew the ageing 30-year-old North-South Line.