Transit Crime Investigation Unit detectives have released additional images as part of their investigation into a sexual assault on a train last year.
A 51-year-old woman boarded the city-bound train at Thornbury Railway Station about 9.35am on 16 May 2018.
She was followed onto the carriage by a man, who repeatedly harassed and sexually assaulted her.
The woman moved away several times before exiting the train at Flagstaff Railway Station, where the man continued to follow her and try to engage her in conversation.
She alerted staff at the station and the man fled the scene.
Investigators have today released two additional images of a man who they believe may be able to assist with their investigation.
The man is perceived as Asian or Pacific Islander in appearance, aged 20-25 years old and about 160cm tall with a medium build.
Police have previously released images and CCTV vision of a man who they wish to speak to in relation to the incident.
At the time he was wearing a New York Yankees cap, denim jacket with a black and white hoodie underneath, tan-coloured pants and dark shoes.
Those images have also been re-released in the hope someone recognises the man.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au