Officials say 2.5 million credit cards could be at risk after a security breach at Michael's Craft Stores.

About three months ago, Michael's announced a breach affecting customers at some of its stores as well stores of its subsidiary, Aaron Brothers. The hack happened between last May and this past January.

The company now says hackers used highly sophisticated malware to steal credit information. Out of the 13 craft stores on Long Island, the company says all of them except for its Valley Stream location had credit card numbers stolen.

Despite the large number of accounts involved, Michael's says it has received "limited" reports of fraud. It says the breach has been contained and all the malware has been removed from its credit card readers. The company is offering a year of free credit monitoring for any affected customers.

Financial crimes expert Diane Peress, from the Nassau County District Attorney's Office, says Michael's is just the latest on a list of major retailers which have been attacked recently. She says people who shopped at any of the hacked stores should watch their statements carefully, ask for a new card from their bank and accept any offers for credit monitoring.