Police in Cleveland are investigating the passing of counterfeit $20 bills at a business here.

Vakarshia Pearson, a Radio Shack clerk, said she noticed the fake bills as she counted money in the store register in preparation for a shift change on Monday.

Pearson told investigators she was unsure which customer had handed her the $20s.

Investigator Robert Graham said fake money collected by law enforcement is turned over to the U.S. Secret Service, the agency charged with investigating counterfeit operations.

“They compare the bills to check to see if they are coming from one source,” Graham said. “A lot of the time it is a serial number that is copied. There might be several bills with one number if they are coming from the same place.”

Though counterfeit bills continue to be circulated, Graham said the problem has declined somewhat in Cleveland.

“We have been having some small bills, but it is not as much as it was this past year,” said Graham. “It is still a problem though.”