Nacogdoches police are wrapping up an investigation into some counterfeit bills that were being circulated on Sunday. The fake bills are mostly 20's but a counterfeit $100 bill was what a University Drive shopkeeper noticed. The police were called. An employee followed the suspect's car to the University Mall where police showed up. Officers found several counterfeit bills, a bogus credit card and a computer and printer. Four suspects from Mesquite were arrested. The Secret Service has been contacted. That agency will continue the investigation with Nacogdoches police.