In its latest Facebook update at 9am, the Singapore Immigration and Checkpoint Authority said arrival traffic remained heavy due to the morning peak period.

In an earlier update, it said buses and lorries were unable to enter the checkpoint as the accident had blocked the heavy vehicle lane.

“Meanwhile, departure traffic is affected due to buses and lorries being diverted back to Malaysia,” it said.

However, traffic for arriving and departing cars and motorcycles was normal as of 7am.

The Straits Times reported that the Singapore Civil Defence Force (SCDF) had responded to a call for assistance at 4.25am as a bus had crashed into the railings.

“A body was found, and there were 16 other casualties conveyed to Ng Teng Fong General Hospital and National University Hospital,” SCDF was quoted as saying.

Photos shared on social media showed that the accident involved a factory bus.