SINGAPORE - Police are investigating a case of criminal trespass that occured on Friday night, leading to train service disruptions on both sides of the North-South Line between Jurong and Yew Tee.

A member of the public had alerted the police to a man allegedly walking on the viaduct between Choa Chu Kang and Bukit Gombak train station on Friday night.

Police confirmed that it received a call for assistance at Choa Chu Kang station at about 8.36pm that night.

Train operator SMRT had tweeted at 9.05pm on Friday calling for commuters to expect 15 minutes of additional travelling time, due to a "track intrusion". It then provided free shuttle services to commuters. About 27 minutes later at 9.32pm, SMRT tweeted that train services were running normally again.

But 12 minutes later, the train operator posted on Twitter that the person "intrudes to the track again". It then stopped train service between Bukit Gombak and Yew Tee in both directions.

Train service only resumed at about 10.30pm.

The Straits Times understands that the man, believed to be acting alone, has not been arrested.