Detectives are investigating after a man allegedly performed an offensive act in Ferntree Gully earlier this month.
Investigators from Knox Sexual Offences and Child Abuse Investigation Team have been told a male inappropriately exposed himself to a pair of 10-year-old girls along the Ferny Creek Bicycle Trail, near the Knox Regional Netball complex, at approximately 4.15pm on Wednesday 12 August.
The male is alleged to have appeared from behind a shelter wearing nothing but purple underpants while staring at the two girls.
Police have released a digital face image of the man in hope that he may be known to someone or they may have seen the incident take place.
He is perceived as being between 30-40 years old, average build, brown hair in a ponytail, a short beard and brown eyes.
At the time of the incident, he was allegedly wearing all dark clothing with purple underpants briefs.
The male police wish to speak to was also allegedly seen riding a black bike and had a black and white bicycle helmet with him.
Anyone who can identify the man or with any information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au.
