Two people died and three were injured in an accident involving a trailer, lorry and three motorcycles at the Causeway early yesterday morning.
A 30-year-old trailer driver has been arrested for suspected drink driving, while a 23-year-old lorry driver has been arrested for allegedly causing death by rash act.
The Singapore Civil Defence Force, which received a call at 1am, dispatched three ambulances and one fire engine. Paramedics pronounced a 21-year-old man dead at the scene.
A police spokesman said three men - the lorry driver, a 37-year-old motorcyclist and a 42-year-old motorcyclist - were taken to Khoo Teck Puat Hospital. The 42-year-old subsequently died from his injuries.
A fourth man suffered minor abrasions and did not want to be taken to the hospital.
The Sunday Times understands that all the men involved are Malaysians.
The 42-year-old, identified as Mr Marrimuthu Subramaniam, was a Singapore permanent resident.
According to Chinese language newspaper Shin Min Daily News, he was a security officer at Certis Cisco and had been married for 18 years, with two sons aged 16 and nine.
He had travelled to and from Johor Baru for work for more than 20 years, according to Shin Min.
Netizen Nasrul Hadi, posting on a Johor Baru traffic Facebook group, described Mr Marrimuthu as a "great guy with a good personality".
Police investigations are ongoing, said the police spokesman.
The accident caused departure lanes at Woodlands Checkpoint to be closed temporarily.
Photos and videos posted on social media showed a lorry crashing across the road divider and into traffic travelling in the opposite direction. Visuals of the aftermath of the accident showed motorcycles strewn along the road, and one underneath a lorry.