LOS ANGELES (CBSLA.com) — Compromised PIN pad devices have been discovered at seven Southern California Barnes & Noble stores.

Barnes & Noble customers were advised Wednesday to change their debit card PIN numbers and review their credit card statements after the bookstore chain discovered a sophisticated criminal operation involving bugged PIN pad devices in 63 of its stores.

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The company says, as of Sept. 14, they discontinued use of all PIN pad devices in all its stores – nearly 700 nationwide. The tampering was a “sophisticated” criminal effort in which a bug was planted to capture credit card and PIN numbers from customers who swiped their cards when making purchases, according to Barnes & Noble officials.

Barnes & Noble officials says its customer and member databases remain secure and that purchases at BarnesandNoble.com, on Nook devices or Nook mobile apps are not affected. None of the compromised PIN devices were discovered at Barnes & Noble college bookstores, either.

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The tampered PIN pad devices were discovered at the following Southern California stores: Calabasas, 4735 Commons Way; Corona, 2470 Tuscany Street; Glendora, 1315 E. Gladstone Street; Montclair, 5183 Montclair Plaza Lane; Redlands, 27460 West Lugonia Ave; Temecula, 40570 Winchester Rd; and Ventura, 4820 Telephone Road.

Customers and employees who have swiped their cards at any of the affected Barnes & Noble stores should take some precautionary steps to protect themselves and their financial information, officials said.

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Debit card users were advised to change their PIN numbers. Customers of the impacted stores were also advised to review their accounts for unauthorized transactions and notify their banks immediately regarding suspicious activity.