Major Collision Investigation Unit detectives are investigating a fatal collision in Heidelberg heights this evening, Victoria Police say.
It is believed a blue Mazda turned onto Bell Street from Upper Heidelberg Road about 5.30pm.
The Mazda has driven onto the wrong side of the road and collided head on with a white Toyota.
A third vehicle collided with the rear of the white Toyota but the single occupant was not injured.
The male driver and female passenger of the white Toyota were taken to hospital with non-life threatening injuries.
The male driver and female passenger of the blue Mazda were taken to hospital in a critical condition, the yet to be formally identified woman has died in hospital.
The exact cause of the collision is still being investigated.
Anyone with information is urged to contact Crime Stoppers.
