"The intrusion was identified by our internal team, it was quickly contained, and we have had no evidence of any misuse of any customer data," Supervalu CEO, Sam Duncan, said in a statement early on Friday.
Supervalu, which had 3,763 outlets as of April, said customers can safely use their credit and debit cards in its stores.
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The company also said it has notified federal law enforcement authorities and is cooperating in their efforts to investigate this intrusion. It has also notified the major payment card brands.
Separately, supermarket chain Jewel-Osco's computers, which contained customer credit cared information, were affected by an "unlawful intrusion," its corporate parent said Friday, according to the Chicago Tribune.
AB Acquisition has not yet determined that any cardholder data was stolen, and it said it has no evidence of any misuse of customer data.
"We understand the inconvenience and concern an incident like this can cause, and we deeply regret that our customers' data was targeted," Mark Bates, Schief information officer at AB Acquisition, told the Tribune.
The company, which operates Albertsons stores under Albertson's and ACME Markets, Jewel-Osco, and Shaw's and Star Markets, said its computers were accessed between June 22 and July 17.
Companies in the United States, particularly retailers, have been targeted by hackers for customer data on payment cards.
U.S. retailer Target is struggling to win back customers after it suffered a huge data breach last year that resulted in the theft of 40 million payment card numbers and 70 million other pieces of customer data such as email addresses and phone numbers.