Are there any real hazards to most muscle-building supplements? (not steroids)

I’ve heard conflicting reports on whether or not muscle-building supplements are harmful to one’s body. The best example is creatine, but there are many others that are also out there. Specifically, I’m looking at Cytocell (which contains creatine, among quite a few others) and Intravol. I’m not looking for personal stories which benefits of such supplements, as there are many to be found all over the web. I’m really looking to see what, if any, real dangers there are to these supplements.