SOUTH BEND (WKZO) -- Police in the South Bend, Indiana area are warning of fake $20 and $100 bills that are turning up in Michigan and Indiana.

Over the past two weeks, there have been at least six incidents where the counterfeit bills have turned up. South Bend police Captain Phil Trent told the South Bend Tribune all of the bills appear to have come from the same source, and all have the same serial number.

The bills look real with a quick glance, but there are things to look for.

The phoney bills have colors that are darker than normal, and the paper is different than that of real currency.

Police ask that anyone with information on the counterfeit bills call Michiana Crime Stoppers at 1-800-342-STOP.