A case of sexual harassment at work

Bronway because sits nervously at your desk, glancing around the room like a cat that has suddenly found herself in the middle of an attack dog kennel. You are the director of human resources for Amalgamated All-Terrain Bikes, Inc., a manufacturer of rugged trail bikes. Bronwyn indicates that she has something very important to tell you and then says nothing. You encourage her to talk, telling her that as director of human resources, you are interested in the welfare of all employees and that if something important is going on, you need to know about it.
Finally the story begins to come out. Bronwyn works on the 3:00 to 11:00 pm shift in the welding area. Several of the male employees who work with her have been giving her quite a bad time lately. As Bronwyn describes it, "They constantly tease me about my ya know, my, uh, shape. They make weird gestures with their hand and laugh like someone has told them the funniest joke they've ever heard. I thought it was just sort f silly at first, but things seem to be getting a bit out of hand. I'm starting to dread coming to work. The guys just don't know when to late something drop-ya know, stop it."
She continues telling her story, with even more disturbing revelations, and states, "I'm really getting sick of it. They bug me all the time. Tease me. Give me all kinds of trouble. They've started pulling some pretty nasty practical jokes on me. Last night I found a balloon filled with silicone in my locker. It really made memad. I'm particularly upset because I know these guys have been doing some other weird things at work, and I've kept my mouth shut. .... Let's just say that by the time they leave this job they'll have had enough experience with drugs to start their own pharmacy! They should all be fired!"
You thank Bronwyn for her information and assure her that you will try to deal with this situation in as effective a manner as possible. As Bronwyn thanks you for listening and leaves, you wonder, "Now, just how do I deal with this?" What would you do first? Explain the steps you would take in trying to manage this difficult situation?