The incident occurred not far from the scene of Eurydice Dixon’s rape and murder.
CCTV footage shows the woman was separated from her friend, who entered a nearby convenience store, when she was approached by three men who pulled up in a ute on the corner of Lygon and Grattan Street at around 4am, the ABC reports. They spoke to her and then got back in the car and drove away.
A fourth man was then caught speaking to the woman on CTV, before he walked away.
Police say she was then taken in a vehicle towards the northern suburbs, during which she was the victim of “serious sexual assault,” Detective Inspector Steve Wilson said.
“Along that journey she was sexually assaulted by one or more persons. We don't know at this stage how many," he said.
The woman’s partner took her to hospital when she arrived home, and the police were notified, The Age reports.
Police say all four men are being treated as witnesses and have called for them to come forward.
“[We want to know] what they saw, what attracted them to our victim and what happened while they were there," Detective Inspector Steve Wilson said.
Police are also calling for anyone with information or who may have seen something to come forward.