What do I do if I know a sex offender is violating probation?

I have recently become aware that a sex offender (whom is not allowed to have access to the internet) has been using facebook with a false name. I have reported it before, but since he has no actual picture of himself on the page, they havent done anything about it. There has to be a way I can give his probation officer a heads up. Its extremely unsettling knowing that he is able to just avoid the law like this. I feel like it would be inappropriate for me to contact the police directly, but if anyone is aware if that is the right step I guess I'm willing to try. does anyone have any advice for me? I would really appreciate it.