Mandan Police say they have now found a sixth counterfeit $100 bill that has been passed in town.
On May 25, a person of interest used the bill at Walmart to do a money transfer to another state.
Bismarck Police are also dealing with several cases. They say counterfeit bills feel different than the real ones, and they fall short when comparing the security features.
"Its just important that people who handle money, really take a quick look at the money if it feels different, you might want to inspect it a little bit more and look for the security features that U.S. Secret Service has listed on their website because you may come across it," says Lt. Patrick Haug, Bismarck Police Department.
Haug says they have a suspect and surveillance footage to help the investigation.