Students and faculty members at Oregon State University have been warned to stay alert after secretly filmed videos of women walking on campus were discovered on a porn website.

More than 50 videos showing women from behind have been uploaded to the site, the university wrote in a Facebook post on Thursday.

All appeared to have been recorded on the university's main campus in Corvallis in recent weeks.

The statement explained that OSU's Department of Public Safety had received tip-offs from two people about the videos, and emphasized that the women's faces were not visible. Those featured in them were not identified by name on the site.

Speaking to OSU's student newspaper,vice president of university relations and marketing Steve Clark said, “Placing photos on the web is not illegal. Inappropriate behavior that puts members of the community at risk can be a student conduct matter, if this is a student, but we don’t know that it is.”

The university advised people to watch out for "an individual appearing to take unsolicited videos of people walking on campus or a person following others walking a silver blue mountain bike with a phone in hand."