The company launched an investigation after it was alerted that some people who used their credit cards at the stores later reported possible fraudulent activity.
Federal law enforcement and data security experts are trying to confirm if the arts and crafts retailer's systems were compromised. Michaels says the company is investigating, but it has not disclosed if and how the breach occurred.
"Throughout our 40-year history, our customers have always been our number one priority and we deeply regret any inconvenience this may cause. The privacy and security of our customers' information is of critical importance to us and we are focused on addressing this issue," the company said in a statement.
Michaels Stores' CEO, Chuck Rubin, is asking customers to check financial statements for fraudulent activity. Customers who see suspicious charges on their statements were advised to report them to their credit card companies and call Michaels at (877) 412-7145.