Two teenagers have been killed and two young boys seriously injured in a crash involving at least two off-road motorbikes in Melbourne’s outer west overnight.

An 18-year-old woman died at the scene and a 17-year-old boy later died in hospital, while two younger boys aged 6 and 11 suffered serious injuries following the devastating crash at Grangefields.

Detective Senior Sergeant at Victoria Police, Paul Lineham, gave some details on the horrific crash and provided an update on the two young boys in hospital.

Press PLAY to hear the latest from police

Press PLAY to hear the initial details from police earlier this morning

Investigators have been told at least two off-road motorbikes and potentially a quad bike were being ridden on Beattys Road when the crash happened around 6:30pm last night.

A 43-year-old Altona Meadows was also injured in the crash and is in hospital with non life threatening injuries.

Police are investigating the circumstances surrounding the incident and are calling on witnesses to come forward.

Image: 9News