What would you do if you suspected fraud was taking place at your company? You could ignore it and hope it wasn't true. You could investigate it yourself and potentially open the company to liability. You could even report it to law enforcement and hope they investigate it.
The best course of action is to report the suspected fraud to your loss prevention team, gather as many details about the fraud as possible without confronting the suspect(s), and hire a
fraud examiner to conduct an investigation.
The outside examiner will be neutral, above internal politics, and not emotionally connected to anyone in the company.
They will conduct a probe, interview witnesses and suspects, obtain a confession and resignation, and often procure restitution. They'll also help you close gaps in your risk prevention program.