Iowa-based grocer Hy-Vee announced Wednesday, Aug. 14, that it is investigating a security breach involving payment card transactions at its fuel pumps, drive-through coffee shops and restaurants.

“After recently detecting unauthorized activity on some of our payment processing systems, we immediately began an investigation with the help of leading cybersecurity firms. We also notified federal law enforcement and the payment card networks. We believe the actions we have taken have stopped the unauthorized activity on our payment processing systems,” the company said on its website.

The company said it appears fuel stops, drive-through coffee shops and restaurants, including Market Grilles, Market Grille Expresses and the Wahlburgers locations that Hy-Vee owns and operates, might have been targeted since they all have a different payment system than the grocery stores, drugstores and convenience stores, which have encryption technology for processing payment card transactions.

Further details about the breach were not immediately available, but the company said it will notify customers as soon as it gets specifics on times and locations that might have been involved.

Hy-Vee, which operates more than 260 stores in eight Midwestern states, including Minnesota, South Dakota and Wisconsin, said customers should immediately report any unauthorized charges to the financial institution that issued the affected card.