The incident took place around 7am, at the AYE stretch along the Jurong Town Hall Road exit towards Tuas.
It involved 4 vehicles – a minibus, a lorry and 2 cars.
The lorry reportedly switched lanes then braked to avoid hitting a motorcyclist.
That resulted in the chain collision with the other 3 vehicles.
Ten passengers on the minibus and 1 from the lorry were sent to hospital.
The accident caused a traffic jam that stretched to Buona Vista and lasted several hours
Police are investigating the incident.