Transit Crime Investigation Unit detectives are appealing for public assistance after a man was allegedly committing a lewd act on the rail network last month.
Investigators have been told the man was first seen performing the act at Southern Cross Railway Station before boarding a Craigieburn bound train about 3.30pm on 26 October.
It is alleged the man continued the act on the train with young children present.
Investigators have released images of a man they believe could assist with their enquiries.
He is perceived to be 25-35-years-old, thin build with black hair and trimmed beard.
Anyone who witnessed the incident or has information that could assist police in identifying the man is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au
