Nunawading Highway Patrol officers are appealing for dash cam footage following a collision in Vermont South on 7 December, Victoria Police say.
It is believed a motorcycle was travelling along Burwood Highway, between Mountain Highway and Morack Road, when it swerved to avoid a beige or light-coloured van and struck a 2011 grey Holden Cruze sedan about 8.20am.
The rider and pillion passenger both suffered serious injuries and were taken to hospital.
The driver of the Holden was not injured in the crash.
Police are keen to chat to the unknown driver of the beige or light-coloured van and urge them to come forward to police.
Police are yet to establish the exact cause of the collision and are appealing for anyone who witnessed it, or who may have dash cam footage, to contact Crime Stoppers.
