NEW YORK – Barnes & Noble Inc. said Tuesday that devices used by customers to swipe credit and debit cards have been tampered with in 63 of its stores in nine states.

The company warned customers to check for unauthorized transactions and to change their personal identification numbers, or PINs. It didn't say how many accounts may have been compromised.

But The New York Times, citing a high-ranking company official it did not name, reported that hackers had made unauthorized purchases on some customer credit cards.