UPDATE, Sunday 10.45am:
A woman in her 40s flown to a Melbourne hospital after a collision near Garvoc is expected to recover from significant injuries.
Senior Sergeant Bill Caldow said the woman suffered broken legs among a range of injuries.
She was driving a Holden Commodore utility which was involved in a collision with a light truck about 1.15pm Friday on the Princes Highway west of Garvoc.
Police are investigating the possibility that the Commodore utility suffered a mechanical fault.
Anyone with information or dash camera footage is requested to contact Crime Stoppers on 1800 333 000.
Friday, 4.30pm: A woman suffering life-threatening injuries has been flown to a Melbourne hospital after her car and a truck collided at Garvoc on Friday.
The accident happened on the Princes Highway just after 1.15pm.
"The driver of the car, a woman believed to be in her 40s, has been airlifted to hospital with life-threatening injuries," a police spokesperson said.
An Ambulance Victoria spokesperson said the woman had been taken to the Royal Melbourne Hospital in a serious but stable condition with chest and head injuries.
The passenger in the car, a teenage male, received minor injuries and was taken by road to Warrnambool hospital.
The driver of the truck, a man believed to be in his 40s, was taken to hospital with minor injuries.
The exact circumstances of the collision are unknown and the investigation is ongoing, police said.
Anyone who witnessed the incident or with dash cam footage is urged to contact Crime Stoppers on 1800 333 000 or make a report at www.crimestoppersvic.com.au
The Princes Highway has reopened between Allansford and Terang but a reduced speed of 60 km/h will remain in place for the weekend.
EARLIER: Emergency services are at the scene of a two-vehicle collision at Garvoc with an air ambulance likely to transport a woman.
The Princes Highway is closed in both directions between Allansford and Terang due to the incident.
Early reports are that a car and a truck collided on the Princes Highway, west of Garvoc, just before 1.15pm on Friday.
A driver, a woman aged in her 40s or 50s, was trapped in one of the vehicles and has head and chest injuries, while a teenage male has minor injuries.
An Ambulance Victoria spokeswoman said the woman was in a stable condition and the air ambulance was on route.
The highway has closed in both directions between Great Ocean Road, Allansford, and Ayresford Road, Terang, due to the collision.
The Department of Transport has advised motorists to detour on the Great Ocean Road, Cobden-Warrnambool Road and Ayresford Road.
"There is limited local access available, under the direction of emergency services," a statement said.
"This closure is under Victoria Police control. The road will reopen when investigations are complete and it's safe to do so."
Three CFA units from Framlingham, Garvoc and Panmure brigades attended the scene.
"The patient was extracted and the scene was declared under control at around 1.55pm," a CFA spokesman said.
Firefighters have conducted a washaway and applied sand to any spills on the road.
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