ST. LOUIS – Schnuck Markets revealed earlier this week that a security breach at its stores compromised up to 2.4 million credit and debit cards as customer data was on its way to the card processor, St. Louis Business Journal reports.

Hackers had installed malicious software into the grocer’s processing equipment, according to Lori Willis, the company’s director of communications.

Schnucks officials said 79 out of 100 stores were compromised from December 1 through March 31. The breach involved card numbers and expiration dates, but not customer names or addresses. 

On March 15, Schnucks learned that 12 cards had been compromised. After launching an investigation, it announced March 30 that the breach was “found and contained.” 

Already, the grocer has been hit with two lawsuits over the breach.