PORTLAND, Maine — Maine credit unions are warning that a breach at a retail food chain popular in New England has the potential to bring them more card fraud than did the massive breach at the TJX retailer.

The Hannaford Brothers grocery chain has reported that during "routine card authorizations" approximately 4.2 million card numbers were exposed. It is not yet clear whether the breach also compromised personal identification numbers attached to the cards. The U.S. Secret Service confirmed that they are investigating the breach but declined to give additional details.

"Because the compromise occurred at a major Maine retailer that so many Maine people use on a regular basis, the impact and cost of this compromise will be significantly higher than the TJX compromise last year," explained Rebekah Higgins, Card Services Manager at Synergent, the service subsidiary of the Maine Credit Union League which handles card services and processing for many Maine credit unions.