U.S. supermarket chain Supervalu Inc. is investigating a potential data breach that could have affected more than 1,000 of its stores, the Wall Street Journal reported on Thursday, citing people with knowledge of the matter.

The data breach appears to have taken place in late June or early July and may be due to malicious software installed by hackers on the retailer's point-of-sale network, the people told the Journal.

Rival Target Corp. 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.

Supervalu had 3,763 stores as of April, according to a regulatory filing.

Supervalu was not immediately available for comment.