The retailer confirmed that several employee bank accounts had been compromised due to the tampered credit/debit card readers in Verifone-supplied self-checkout terminals.

In a statement, SaveMart says: "There have been approximately 80 employee and customer reports of either compromised account data or attempts to access account data, with the majority coming over this past weekend."

The chain picked up on the breach during routing maintenance in November. It has yet to ascertain timelines for the incident.

"We strongly recommend our customers who used a self check-out lane in the affected stores contact their financial institution to close existing accounts and seek further advice," says the company. "We continue to work with local, state, and federal law enforcement to find those responsible."

In May, US retailer Michaels Stores reported that 90 PIN pads at its shops around the country had been tampered with, leaving customer card details at risk.