Where does a citizen report possible fraud for claiming insurance work injury?

Question

Where does a citizen report possible fraud for claiming insurance work injury?

Answer 1

Each state insurance department has a fraud department.  Some of them, you can even report online (others you need to do it via telephone or in writing).  

So go visit your state insurance department website, and use keyword "fraud".

Answer 2

You could send an anonymous not to that person's employer.

Also contact your state's Workman's Compensation Board.