Last month police made a public appeal for information including a search for three men who assisted the victim following the incident.

One of these men subsequently contacted police, however the two other men are still outstanding.

A woman in her late teens wearing a black jacket was walking along Flinders Street towards Swanston Street to catch a tram shortly after 1.45am on Saturday, 9 June.

As she walked past a bar situated below a hostel between Elizabeth Street and Degraves Street, a man exited the building and started to walk alongside her.

He then placed his arm around her shoulders and neck and engaged her in a short conversation as they continued to walk towards Swanston Street.

As the pair approached the Metro Tunnel works, the man pulled the woman to him and kissed her.

She pushed him away and continued to walk towards Swanston Street, however the man kept his arm around her shoulders and neck.

Once they passed the works, the man dragged the victim into an alleyway behind high metal gates, locked the gates, then sexually assaulted her.

The woman managed to scream and was able to run away from the man and out the gates on to Flinders Street.

Police believe a number of people saw her running from the scene along Swanston Street to Flinders Lane as the area was still quite busy.

At Flinders Lane, three males approached the woman to assist as she was visibly distressed.

They were able to help her contact a friend and arrange transport home.

Detectives understand the woman did not tell the males she had been sexually assaulted.

Police are today releasing footage and images of a man they believe may have possibly spoken with the victim around the time of the incident.

Detectives are hoping the man will be able to come forward and provide them with information that will assist the investigation.

They would also like to speak to anyone who can identify this man.

He is described as being African in appearance and was wearing a black puffy jacket with red lining, light blue jeans and white runners.

Investigators have also re-released images of the two male good Samaritans who are yet to come forward.

The investigation into the sexual assault remains ongoing and police are still searching for the man involved in the incident.

He is described as being aged in his early 20s, around 178cm tall with a lean build, dark brown skin and short hair.

At the time of the incident he was wearing a dark coloured jacket and long pants.

Anyone who recognises the witnesses or has any information about the incident is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au.

Photo: vicpolicenews