Investigators in West Bend said two, high-profile skimming incidents there this year have impacted about 100 of the city's residents.
"To have somebody, or a group, affecting this many people at once is unusual," said Lt. Paul Pokorski, of the West Bend Police Department.
Back in January, investigators arrested Yosdanky Llanes Perez and Pedro Ivan Vazquez Gutierrez.
According to a criminal complaint, the two men bought gift cards and small items at Walmart stores, totaling more than $700, using credit card information stolen from several West Bend residents.
Police said the men obtained the stolen information after installing a skimmer in a local gas pump.
Pokorski said the skimmer was installed inside of a gas pump so that customers wouldn't see it. But he said the device was routing information about their credit cards from inside of the pump to a computer found in the possession of the two suspects.
"Primarily with help from the FBI, they were able to take info off of the skimmer itself and connect it to the computer in their possession," Pokorski said.
Both men were found guilty and sentenced to 12 months in the local jail. Vazquez Gutierrez is in the United States illegally.
Pokorski estimated the two men, who told investigators they'd been living in Florida, defrauded 437 victims in several states.
"We believe they were doing the same type of thing all the way, along the way, from Florida to Wisconsin," he said.
In the spring, West Bend Police flagged two more skimming suspects: Yoisel Cristobal Gomez Reinoso and his brother Lazaro Yadir Gomez Reinoso.
Both men, of Florida, were extradited to Wisconsin and are now awaiting trial here.
Pokorski said the two men are accused of defrauding 36 residents, through 95 phony charges, in April and May. He said the total money taken was estimated at $16,000.
Pokorski said the fraud was traced back to a local gas pump, after several victims reported swiping their cards at the pump before the identity theft began to show up on their card statements.
One of the cards compromised was the Police Chief's department-issued fuel car. The skimmers used that information to buy $900 worth of diesel fuel at gas stations in Florida.
"It can happen to anybody, at any time," Pokorski said.
Both of the Gomez Reinoso brothers are due back in court next month.