I want to report someone for selling drugs can I do it anonymously?

What my question is basically is is it possible for me to report a drug dealer anonymously without being called in for questioning by the FBI or police department, and will the police at least investigate it or will I need to provide some kind of direct evidence before they do, and would I have to divulge my identity to the police at some point, and if they can't prove the allegations could I be in legal trouble since I reported the crime?