Transit Crime Investigation Unit detectives are appealing for public assistance following a sexual assault at Newport Railway Station last month, Victoria Police say.
A 17-year-old girl was at the station about 2pm on 1 May and was on her way home from school.
She walked down the ramp to exit the station and was approached from behind by an unknown female, who sexually assaulted her.
Investigators have released CCTV and an image of a female they believe may be able to assist with their enquiries.
The female is described as aged in her 30s with brown hair tied in a bun with a tattoo or writing on her right thigh and a lower back tattoo.
She was wearing a black singlet, black shorts, black thongs and had a white long sleeve top draped over her shoulders.
It is believed the female may have been at the railway station with a man perceived to be Caucasian, wearing an Essendon Bombers baseball cap, an open dark coloured shirt over a red t-shirt and dark coloured pants.
Anyone with information is urged to contact Crime Stoppers.
