One woman was killed and 16 other people were injured after their bus collided into a railing at the Tuas Checkpoint early yesterday.
The 35-year-old victim was pronounced dead at the scene by paramedics, said the Immigration and Checkpoints Authority (ICA).
The bus driver, 59, was arrested for causing death by a rash act, police said.
The accident blocked the heavy vehicle lane from about 4.20am, causing traffic to pile up, as buses and lorries bound for Singapore were unable to enter the checkpoint. The ICA subsequently closed the lane and the heavy vehicles were turned back to Malaysia.The lane was reopened at about 10am.
Responding to a call for assistance, Singapore Civil Defence Force (SCDF) officers arrived at the accident scene in Jalan Ahmad Ibrahim to find the bus against the railing and the driver trapped in his seat. He had to be rescued using hydraulic equipment, SCDF said.
Two women were found outside the bus. One was pronounced dead and the other suffered serious injuries.
The driver and 11 passengers were taken to Ng Teng Fong General Hospital and National University Hospital. Four other passengers with minor injuries declined to be taken to hospital.
Three passengers were hospitalised and the rest discharged.
Confirming that some of its employees had been on the bus, a spokesman for technology company HP said: "Our thoughts are with those who were involved, and we are doing everything we can to provide assistance to affected employees."
Mr Dia Abdullah, 28, who was headed to work, told The Straits Times that it took him 1½ hours to get through the checkpoint because of the traffic jam. It usually takes about 30 minutes at 5.30am, said the operations executive.
"The traffic is usually clear for cars at that time but we were not able to move, as they stopped us and were allowing buses and lorries to make a U-turn back to Malaysia."
One victim, understood to be an HP employee, was sitting in the middle of the bus when the crash occurred.
"Everyone was sleeping when it happened, and we were woken by a strong impact. My arms and legs were hurting, and it was very chaotic," Ms Vani, 43, told Chinese daily Lianhe Wanbao.
The bus appeared to have had braking issues before it hit the railing, she said, and many of those injured were cut by broken glass.
• Additional reporting by Jev Akshay Jeevan