The devices were found at self-checkouts at various locations in Montgomery County, including Kulpsville, Upper Gwynedd and Collegeville.
Collegeville Police and 6abc reported numerous credit card skimming devices were found at self-checkout registers inside numerous Royal Farms locations in Montgomery County.
According to reports, six Royal Farms stores had the devices, including the Upper Gwynedd, Kulpsville and Collegeville stores.
Authorities in the affected areas are trying to figure out when the devices were installed and urge customers to check card activity.
Police advised customers use contactless payment options, or cash.