(Bloomberg) – Staples Inc., the world'slargest office-supply chain, is investigating a potential breach ofcustomer credit-card data, becoming the latest retailer to confronta threat from hackers in recent months.

Staples has contacted law enforcement authorities andis working to resolve the matter, according to Mark Cautela, aspokesman for the Framingham, Massachusetts-based company.

"If Staples discovers an issue, it isimportant to note that customers are not responsible for anyfraudulent activity on their credit cards that is reported on atimely basis," he said in an e-mail.

The potential data theft adds to a wave of breaches at companiessuch as Home Depot Inc., Target Corp., Sears Holdings Corp.'s Kmartchain and Neiman Marcus Group Ltd. that have put pressure onretailers to bolster security.The Staples incident, reported earlier byindependent journalist Brian Krebs, may involve the theft of cardinformation from Staples locations in theNortheast.

Staples declined 1.1% to $12.17 at 9:55 a.m. in NewYork. The shares had dropped 23% this year before today, comparedto a gain of 3% for the Standard & Poor's 500 Index.

At least three stores in New York, seven in Pennsylvania and onein New Jersey may have been targeted, according to unidentifiedofficials at banks in the East Coast cited by Krebs, whoinvestigates hacker attacks. The fraudulent charges occurred atother businesses such as supermarkets, indicating that cashregisters in at least some store locations may have fallen victimto card-stealing malware, Krebs reported yesterday.

Retail Slump

The data-breach probe comesas Staples grapples with a broader retail slumpand increased competition from online rivals. In August, thecompany announced it will shut about 140 locations this year aspart of a plan to streamline its operations.

Staples shut 80 outlets in North America in the fiscalsecond quarter. Net income last quarter dropped 20% to $82 million,or 13 cents a share, as $101 million was spent on closinglocations, the company reported in August.

Expansion by Web-based rivals such as Amazon.com Inc. hasspurred reorganizations across the retail industry, including themerger of Office Depot Inc. with OfficeMax Inc.

–With assistance from Suresh Seshadri in Bengaluru and MattTownsend in New York.