Hamilton Police have arrested one man and are looking for three more after investigating a string of sexual assault allegations at McMaster University that prompted female students to take to social media to share information.

Police have arrested a 19-year-old Oshawa man on five counts of failing to comply with recognizance and two counts of breach of probation after incidents on April 8 and 9. Police haven't charged the Oshawa man with sexual assault, but say that investigation is continuing.  Police are opposing his bail.

"It is believed that three other males may be involved in the sexual assaults," Hamilton Police say.

The arrests appear to reference the same events as a flurry of social media posts and warnings on the "Spotted at Mac" Facebook page after the end-of-term Light Up the Night event on campus on April 8.

Police said at the time that they were investigating one sex assault in a washroom in the Burke Science Building and four other complaints of "unwanted, non-consensual touching."

The Facebook posts didn't make it clear if there was a group or single person harassing the women. The posts talked about being approached and when the women rejected the conversation or advanced, they faced unwanted touching and/or harassment.

Several posts suggested the same man or men harassed women on Instagram and Snapchat, on the bus and at other locations in the city.

"These guys are not only around Mac, they are also around Hess on Friday nights and Saturday," reads one post. 

In some posts, there were descriptions of the men along with ways women can protect themselves.

"These complaints have been going on for a lot longer than just a few days," said a post.

The police victims of crime unit is working with McMaster University Security Services, police say. Anyone with information should call Det. Jason LEEK at 905-546-8958 or Crime Stoppers at 1-800-222-8477.