Detectives from Major Collision Investigation Unit are appealing to the public to help assist their investigation into a fatal crash in Balliang East on Friday 13 December.
Investigators believe a metal towing component fell from an unknown vehicle travelling north on the Geelong-Bacchus Marsh Road about 2.15pm.
It is believed a white b-double tip-truck also travelling north ran over the towing component and caused it to flick up into the path of a grey Hyundai SUV driving in the opposite direction.
The object entered through the windscreen of the Hyundai striking the driver.
The vehicle continued for approximately eighty metres before running off the road striking a tree and rolling.
The female driver, a 37-year-old Jan Juc woman, died at the scene while her infant son who was a passenger was taken to hospital with minor injuries.
Detectives are keen to speak to the driver of a vehicle who may have been driving on Geelong-Bacchus Marsh Road at the time and is missing a towing component and the driver of the white b-double tip-truck.
Anyone who witnessed the crash, has dash cam footage or any information is urged to contact Crime Stoppers on 1800 333 000 or visit www.crimestoppersvic.com.au