Bacchus Marsh crash: homicide detectives investigate after motorcyclist killed

Homicide Squad detectives are investigating following the death of a motorcyclist who died in an alleged hit-run collision north-west of Melbourne last night.

Emergency services were called to Woolpack Road at Maddingley, near Bacchus Marsh, after reports a motorcyclist was struck by a ute about 7.15pm.

The man, who is yet to be formally identified, died at the scene.

The male driver of the ute, with two passengers inside, allegedly failed to stop at the scene and drove further down the road before pulling over.

The driver and one of the passengers were assisting police with enquiries.

A manhunt is underway for the second passenger who fled the scene on foot.

"It is a joint investigation with MCIU [Major Collision Investigation Unit], local police and the Homicide Squad due to certain circumstances that have been alleged at that crash," Victoria Police Deputy Commissioner Shane Patton said.

"My understanding is they have been involved and are known to each other."

The exact circumstances surrounding the collision are yet to be determined and the investigation remains ongoing.

Police are keen to speak to anyone who witnessed the incident or has dash-cam vision of the vehicles in the lead up to the collision.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000.