Six young men killed or critically injured in a "catastrophic" head-on crash in Melbourne's west were not wearing seatbelts, police believe, including the unlicensed teenage driver.
The sedan had six young males, believed to be aged between 15 and 20, on board when the driver lost control and collided with a small truck at Truganina on Thursday night.
Two of the males died at the scene and another two on their way to hospital, while the others continue to fight for life in hospital.
The truck driver was also taken to hospital for observation.
Assistant Commissioner of Road Policing Glenn Weir described the crash as "catastrophic" and said he believed the driver was among the dead.
"It looks as though the male who was driving the car was around 16 years of age. Obviously without a licence (and) obviously extremely inexperienced," he told reporters on Friday.
"Last night's weather was really challenging. There are suggestions of speed and inappropriate driving."
None of the occupants of the car are thought to have been wearing seatbelts at the time of the crash, to the frustration of police.
"It's just an absolute recipe for disaster," Mr Weir said.
"I know these were kids but there are some basic common-sense things that people have to follow and they haven't been followed in this case."
Mr Weir said police do not believe the car was stolen but are working to contact its registered owner who lives overseas.
Victoria Police's Major Collison Investigation Unit detectives are investigating the circumstances of the crash, which occurred metres from homes.
The coroner has been notified and Mr Weir said police were open to working with the transport department or local government to make changes to the road, including reducing the speed limit.