Frankston Crime Investigation Unit detectives are appealing for public assistance following a robbery in Frankston in February.
Investigators have been told a teenage boy was approached by a group of eight male teenagers and a teenage woman at a Shannon Street mall about 5.30pm on 15 February.
One of the males assaulted the victim and stole his phone before the group, who were all perceived to be of Maori or Pacific Islander in appearance, fled on foot.
The victim, a 15-year-old boy, did not require medical treatment.
Detectives have released images of a female who they believe will be able to assist with their enquiries.
She is perceived to be Maori or Pacific Islander in appearance and aged in her late teens.
She was wearing a grey NY t-shirt and ripped black skinny jeans; and was carrying a black Nike bum bag with a small dog toy plushies keyring attached.
The investigation remains ongoing and anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au