Detectives from the Sexual Crimes Squad are appealing for information following a sexual assault at a B&S Ball in Winnindoo last month.
Police have been told a 24-year-old woman went to one of the portable toilets around 50 metres from the stage at the Rices Lane function about 11pm on Saturday, 15 November.
When she entered the toilet, a man followed her in from behind before sexually assaulting her and then fleeing the area.
She then attended first aid to report the incident and police were called.
A second sexual assault is believed to have occurred on the dance floor around 1.15am.
Police spoke to a man on the night in relation to the second incident, however at this stage, it is not known if the two incidents are related.
A number of items have been seized in relation to the initial sexual assault and they have been forensically tested.
The area was not covered by CCTV, but police are urging anyone who has any photos or vision from the portable toilet area around 11pm to submit them online via Crime Stoppers.
Investigators are appealing for anyone who may have witnessed any strange or suspicious behaviour around the portable toilet area to come forward and speak to police.
Police are currently working through a list of people who bought tickets and who subsequently attended on the night.
Victoria Police encourages all victims of sexual assault and child abuse, and anyone who has knowledge of such a crime, to make a report.
Anyone with information that could assist police is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au
Quotes attributable to Detective Inspector Mark Burnett, Sexual Crimes Squad:
"We know that those who attend B&S balls are generally a tight knit community. If you witnessed anything odd that night - someone loitering around the portable toilet area, following women or perhaps trying to open the doors of already engaged toilets, then please, come forward and speak to police.
"Whilst we don't have a solid description to provide of the man we'd like to speak to, forensic samples have been obtained and our investigators are strategically making their way through a list of those who bought tickets to the event and those who attended on the night.
"If you have information about either of these sexual assaults, it is time to do the right thing and come forward."
