ONAMIA — Grand Casino Mille Lacs is investigating a data breach.

Casino officials said they learned in September that some payment cards were used at the Onamia location for fraudulent transactions.

Officials believe that the suspect used malware to access certain payment card transactions made between April 24 and Oct. 9.  The information that may have been accessed includes customers’ names, payment card numbers and card expiration dates.

The incident is limited to about 1,600 card transactions.  So far, officials have no evidence that any additional cards are at risk.

Grand Casino Mille Lacs has posted a website notice and has a toll-free phone number — 866-328-1987 — for customers with questions.