Four of the locations were in Montgomery County and two were in Delaware County, including one on the 2100 block of West Chester Pike in Broomall.
"It's kind of jacked up. Because people out here, we work hard for our money," said Erik Bennett from Collingdale.
Erik Bennett changed his plans once he learned a skimming device was found.
"Now I know I'm gonna go in here and pay in cash," he said.
Marple Township police say the store found the device over the weekend.
"We found out because the manager had discovered another one at a location in Montgomery County somewhere," said Marple Township Police Chief Barndon Graeff.
So far, there are six confirmed Royal Farms stores where the devices were found, including Glenolden, Broomall, Collegeville, Norristown, Kulpsville, and North Wales.
Collegeville police put out this picture of the device. Investigators say it's a gadget that fits over the card reader and steals credit and debit card information.
At this point, police in all six townships are still trying to figure out exactly when the devices were installed but are urging anyone who visited the stores to monitor their card activity.
"Check your statements, check your credit card statements, check your bank statements and notify your financial institution, even before you notify us," said Graeff.
Some Royal Farms customers were shocked to learn about the crime.
"Impressive. They're organized," said Roberta Snow from Drexel Hill. "It won't keep me from buying the chicken, that's for sure."
Police say there are ways to protect yourself. If you're using a card, use contactless payment options, or better yet, just use cash.