RCMP say payment PIN pads like this one were tampered with in a skimming operation discovered at a mall near Calgary. ((CBC))

A suspected bank card skimming operation has been uncovered at the CrossIron Mills mega-mall near Balzac, north of Calgary, police said Friday.

Bank security experts alerted RCMP commercial crime detectives after they found that two payment PIN pads at two retailers had been compromised. Mall officials said police advised them not to name the stores involved.

The pads had been tampered with to capture customers' financial information and gain access to their accounts, said RCMP Const. Lane Menard.

"They'll tap in to the magnetic stripe reader, capture that data, tap in to where the PIN is entered and put that on a memory board," said Menard. "They then load it onto a computer and make counterfeit cards."

A full search of the approximately 200 stores at the mall turned up two more skimming devices, investigators said. The transaction pads were likely installed sometime in July.


Four payment pads at CrossIron Mills mall in Balzac, Alta., had been altered to steal bank and credit card data. ((Mary Sheppard/CBC))

Some unauthorized withdrawals from bank accounts may have already occurred, but investigators think most of the potential fraud was interrupted before it became significant.

The culprits likely swiped the PIN pads while store clerks were not looking, substituting non-functional dummies while they added a wireless Bluetooth transmitter to the devices.

"Then they return later and return that original, and the retailer's totally unaware that it's been compromised," said Menard.

No charges have been laid and the investigation continues.

Police said anyone who may have used a debit or credit card at the mall should check their banking records, police said. They are also reminding the public to keep track of their accounts and to change card PIN numbers frequently.