Transit Crime Investigation Unit detectives are investigating a sexual assault which occurred on a bus between Mentone and Dandenong.
Investigators have been told a 17-year-old girl was travelling on a bus when an unknown man performed a lewd act towards her between 4pm and 5pm on June 9.
The man boarded the bus with another man on Lower Dandenong Rd in Mordialloc around 4pm.
Both men disembarked the bus on Cleeland St in Dandenong around 5pm and left the scene in a southerly direction.
Detectives have released CCTV images of a man they believe may be able to assist with their enquiries.
The man is perceived to be Pacific Islander in appearance, aged between 30-40 years old, with dark hair and a beard.
He was wearing blue hooded jumper.
n Any witnesses or anyone with information is urged to contact Crime Stoppers on 1800 333 000 or make a report online at www.crimestoppersvic.com.au