What would you do?

Say you meet someone and they confide in you that they are an illegal alien and have an "owner" who controls where they live, work, and go. All their food is provided but is very simple. They share a room with someone where they work. They'd like to keep working where they are at but they have no control over it. If they are found out they will be sent home and may starve to death. Do you let sleeping dogs lie or contact the authorities?