TJX ( TJX) said hackers stole customer credit card and driver's license data.

The Framingham, Mass., retailer said it doesn't know the extent of the theft or the number of affected customers. But the company said the "unauthorized intrusion into its computer systems that process and store information related to customer transactions" took place last month.

TJX said the intrusion involves the portion of TJX's computer network that handles credit card, debit card, check, and merchandise return transactions for customers of its T.J. Maxx, Marshalls, HomeGoods and A.J. Wright stores in the U.S. and Puerto Rico, and its Winners and HomeSense stores in Canada.

The theft may involve customers of its T.K. Maxx stores in the U.K. and Ireland, and Bob's Stores in the U.S.

The company said it immediately alerted law enforcement authorities and is cooperating with credit and debit card issuers.

Shares were halted at $29.85 Wednesday.

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