SHEBOYGAN, Wis. (WHBL) - The Sheboygan Police Department is investigating two instances of counterfeit bills in the area.  Captian Jim Veeser said in a news release that both instances happened December 30^th; where two males tried to pass the altered bills at Shopko and Big Lots, both in Sheboygan.  Police say that investigations into similar occurrences are happening in nearby counties.  A 28 year old male has been arrested in Menominee Falls and is believed to have been involved in the Sheboygan incident.  Police are still looking for the other suspect.  Police are asking businesses to be cautious and report anything suspicious to them immediately.