Responding to inquiries about a possible data breach involving customer credit and debit card information, upscale retailer Neiman Marcus acknowledged today that it is working with the U.S. Secret Service to investigate a hacker break-in that has exposed an unknown number of customer cards.

Earlier this week, I began hearing from sources in the financial industry about an increasing number of fraudulent credit and debit card charges that were being traced to cards that had been very recently used at brick-and-mortar stores run by the Dallas, Texas based high-end retail chain. Sources said that while it appears the fraud on those stolen cards was perpetrated at a variety of other stores, the common point of purchase among the compromised cards was Neiman Marcus.

Today, I reached out to Neiman Marcus and received confirmation that the company is in fact investigating a breach that was uncovered in mid-December.

Neiman Marcus spokesperson Ginger Reeder said the company does not yet know the cause, size or duration of the breach, noting that these are details being sought by a third-party forensics firm which has yet to complete its investigation. But she said there is no evidence that shoppers who purchased from the company’s online stores were affected by this breach.

The entirety of the company’s formal statement is as follows:

“Neiman Marcus was informed by our credit card processor in mid-December of potentially unauthorized payment card activity that occurred following customer purchases at our Neiman Marcus Group stores. We informed federal law enforcement agencies and are working actively with the U.S. Secret Service, the payment brands, our credit card processor, a leading investigations, intelligence and risk management firm, and a leading forensics firm to investigate the situation. On January 1st, the forensics firm discovered evidence that the company was the victim of a criminal cyber-security intrusion and that some customers’ cards were possibly compromised as a result. We have begun to contain the intrusion and have taken significant steps to further enhance information security. The security of our customers’ information is always a priority and we sincerely regret any inconvenience. We are taking steps, where possible, to notify customers whose cards we know were used fraudulently after making a purchase at our store.”

The disclosure comes as many in the retail sector are seeking more information about the causes of the breach at nationwide retail giant Target, which extended from around Thanksgiving 2013 to Dec. 15, and affected some 40 million customer debit and credit cards.

Target released additional details about the breach today, saying hackers also compromised the names, mailing addresses, phone number and email addresses for up to 70 million individuals. But Target has so far not publicly released information that would help other retailers determine whether their systems may have been hit by the same attackers.

Neiman Marcus’s Reeder said the company has no indication at this time that the breach at its stores is in any way related to the Target attack. Still, the timing of the discovery of the Neiman Marcus incident — mid-December — roughly corresponds to the discovery of the Target breach. I will have more on this developing story if additional details become available.

Tags: Ginger Reeder, Neiman Marcus breach, target, U.S. Secret Service