Police arrested a man in Mandurah on Sunday afternoon in relation to an alleged sexual assault at a University of Western Australia toilet block.
The incident happened at 8.30am on Saturday morning near Mounts Bay Road in Crawley.
Police stated soon after that the alleged attacker was aged in his 30s and wearing a red striped hooded top and dark pants. He was seen walking on Stirling Highway.
A man was arrested in Mandurah about 4pm on Sunday in relation to the incident.
Anyone with information should call Crime Stoppers on 1800 333 000 or make a report online at crimestopperswa.com.au.