Audit to Forensics?

I am an audit associate at a Big 4 firm in the Midwest.  I like the people I work with and have gotten good client exposure during my first year. Like most of you, I don't think I have a career in auditing.  I would like to eventually get into forensic accounting or fraud investigation.  When should I start to look into moving into an advisory/forensics division at my firm?  Will the opportunities get better if I wait until I'm a senior associate or manager? At that point should I make the jump to private practice?