UPDATE: A motorcyclist is dead after a crash on the Monash Freeway.
All but one inbound lanes remain closed between Warrigal and Toorak roads after the collision between the bike and a truck about 8.20am.
Victoria Police media officer Kelly Yates said it was believed the motorcyclist was struck from behind by the truck.
The truck driver continued driving after the collision, but stopped a short time later, Ms Yates said.
The motorcylist, who is yet to be identified, died at the scene, she said.
The male truck driver is helping police with inquiries.
Emergency services are still at the scene and motorists have been warned to expect heavy delays.
Traffic is being diverted at Warrigal Road onto the Princes Highway.
Anyone with information is asked to call Crime Stoppers on 1800 333 000.
