The Chronicle also quoted executives from the Community Schools Credit Union and Muskegon Commerce Bank who said they took similar actions after discovering fraudulent transactions involving cards issued by them. Representatives from the two banks did not respond to several requests for comment.

Campbell said it remains unclear where the information used to forge the banks' credit and debit cards was obtained.

But suspicions are centered on Wesco, a local gas station and convenience store chain with 51 locations in Michigan. In a note posted on the company's Web site, Wesco said that it is investigating the "possibility of credit card fraud associated with card use at our facilities."

According to the company, credit card transactions that occurred between July 25 and Sept. 7 may have been somehow compromised.

"The U.S. Attorney's office and the U.S. Secret Service have launched an investigation to understand the scope of the problem," the company said. It encouraged those who shopped at Wesco stores to verify transactions with their financial institutions and said that it is "cooperating fully" with federal authorities.