Prosecutors said the victims recently made contact with the scammers, who claimed to be associated with Secret Shopper, a legitimate company that contracts with business clients and pays customers to go to the client's store to evaluate the quality of service there.
The scammers sent the victims large cashier's checks and told them to return $1,700 through Western Union.
The victims were alarmed by the request and contacted the district attorney's office.
People are advised to research companies before making contact with them and to use the online search term "Secret Shopper Scam" for more information about similar scams.
Victims of the scam can also file a report with their local police department, the Internet Crime Complaint Center or the Federal Trade Commission.