It was learnt that the police van was heading towards Lahad Datu from Tawau for a trial at the Lahad Datu court while the Toyota Ninja came from the opposite direction.
District Police Chief, ACP Shamsudin Mat said preliminary investigation found that the van and the Toyota Ninja collided in a corner due to slippery road conditions.
"During the incident that occurred at about 4.30pm, the van was carrying four prisoners and four police personnel.
"Two policemen and a prisoner as well as the Toyota Ninja's driver and his front passenger suffered serious injuries," he said.
Shamsudin said the case was being investigated under Section 43(1) of the Road Transport Act.