Ten cars were involved in a pile-up along the Pan-Island Expressway on Thursday evening.
Four people were sent to hospital after the crash in the direction towards Tuas, after the Paya Lebar exit.
A man in his 50s, a woman in her teens, and two women in their 50s were sent to Tan Tock Seng Hospital with minor injuries, a Singapore Civil Defence Force (SCDF) spokesman told The Straits Times.
The SCDF received a call for assistance at 5.30pm and sent two ambulances to the scene.
It caused a long jam till Jalan Eunos, which the Land Transport Authority tweeted about, to advise motorists heading that way.