UPDATE 6PM: A man in his seventies remains in a serious condition after sustaining pelvic and abdominal injuries in a two-car collision on the Calder Freeway at Harcourt this afternoon.
The man made a U-turn onto the Calder Freeway from the access ramp at Harcourt and collided with a Melbourne-bound vehicle about 3.15pm.
His passenger was treated on scene, and four other people - all aged in their twenties - were transported to Bendigo Health.
Ambulance Victoria spokesman John Mullen said the occupants of the south-bound car had received non-life threatening injuries.
"A male sustained facial injuries, another male has leg injuries, a female has neck and facial injuries and we are unaware of what injuries the other passengers sustained," he said.
"They all remain in a stable condition."
UPDATE 4.50PM: The Calder Freeway at Harcourt has re-opened after a crash this afternoon.
UPDATE 4.20PM: Leading Senior Constable Peter Dyer said a Toyota four-wheel drive had driven off the access lane at the south-bound ramp at Harcourt and attempted to do a U-turn into oncoming traffic.
"He has T-boned into a car with four innocent passengers, who are now all injured," he said.
"The driver and his passenger are from New South Wales and it seems they did not know what they were doing."
EARLIER: SIX people have been injured after a two-vehicle crash on the Calder Freeway near Harcourt.
A vehicle made a U-turn onto the Calder Freeway from the access ramp at Harcourt and collided with a Melbourne-bound vehicle about 3.15pm.
Four people travelling in the south-bound vehicle have sustained non-life-threatening injuries and have been taken to Bendigo Health.
The driver of the second vehicle will be flown to Melbourne with serious injuries. The passenger of the vehicle has non-life-threatening injuries.
Police, CFA and SES personnel are on scene.
The freeway is closed and traffic is being diverted through Harcourt.
More to come.