What component of electronics is produced by slave labor?

[JashimChando]

I learned a few years ago in an Ethics and Social Responsibility class that most electronics, computers and mobile phones have a component that is made using slave labor. I'm not sure whether it's an element that is mined or something else. But I'm sure that such a thing exists and that slave labor is a part of the production line in electronics (it was recently on the news too). Anybody know what that component/ element is?