Luxury department store chain Neiman Marcus said on Friday that hackers may have stolen customers' credit and debit card information, the second cyber attack on a retailer in recent weeks.

The data breach comes after Target Corp. (TGT) on Friday said an investigation found a cyber attack compromised the information of at least 70 million customers, in the second-biggest retail cyber attack on record.

Neiman Marcus does not know the number of customers affected by the intrusion, company spokesperson Ginger Reeder said.

Neiman Marcus said its credit-card processor alerted the retailer in December about potential unauthorized payment card activities and the U.S. Secret Service is investigating.

A third-party forensics firm confirmed the cyber-security intrusion on Jan. 1, the company said.

Reeder declined to comment if the breach was related to the Target cyber attack.