LOUISVILLE, Ky. (WHAS11) -- Something as simple and menial as filling up a tank of gas is now the target of criminals looking to steal credit card information.

"The things people do these days is devastating. I had no idea," Marcy Thorn, a gas station customer, said. "You shouldn't have to come to no gas station and worry about your card or your information being taken."

"The FBI has recently confirmed skimming in a total of 37 states, so we're not alone in this," United States Attorney Russell Coleman said.

The U.S. Attorney's Office in the Western District of Kentucky, the FBI, the United States Secret Service, Louisville Metro Police and other law enforcement agencies across Kentucky, Indiana and Ohio, announced the arrest of eight people charged with aggravated identity theft and wire fraud among other charges for using credit card skimming tools installed in gas pumps, often without people knowing.

"Within a matter of five minutes if not even less," FBI Special Agent in Charge Amy Hess said. "If they did it properly and they did it right, you won't see it as a consumer."

Officials said the investigation, which began in early 2015 after victims came forward about having their credit card information stolen, has estimated more than 7,000 credit card numbers for people and businesses have been affected, with more than $3.5 million believed to be lost.

According to the indictments and plea agreements, local gas stations that were affected included those located on Highway 42 in Prospect, Taylorsville Road, Bardstown Road, Saint Andrews Church Road, Galeen Drive, Shelbyville Road and LaGrange Road.

"If you're monitoring your account and you see a problem, anything you do not recognize as your own purchase, contact the bank and law enforcement right away," LMPD Chief Steve Conrad said.

Officials are encouraging people to be vigilant when going to the gas station - checking to see if any of the U.S. Secret Service and Kentucky Department of Agriculture's seals are broken or tampered with, or if anything looks or feels off at the pumps. People are also encouraged to use gas pumps that are in the line of sight of the gas station attendants, which lowers the chance the pump has been compromised.

According to officials, if people need to pay with a card, they should use the credit card function, which makes it easier for banks to expedite the process of returning money to victims. But officials still say the safest option is to pay the gas station clerks with cash.

"Use cash a little more," Thorn said after learning about the arrests. "I think my card will stay in my purse for a little while."

"It's terribly inconvenient, families with kids in the vehicle, terribly inconvenient, but is the only true failsafe in these cases," Coleman said.

Law enforcement also has another message, one targeted to those hoping to profit at the expense of unknowing victims.

"If you're going to commit this type of fraud, keep on moving down 65 or stay out of the Western District of Kentucky because you will become intimately familiar with the Federal Bureau of Prisons," Coleman said.

“Credit card skimming at gas pumps is a rising threat for Kentuckians. The Kentucky Department of Agriculture is proud to work alongside our friends in the law enforcement community to combat this problem,” Commissioner Ryan Quarles with the Kentucky Department of Agriculture said in a statement. “For the second year in a row, our gas pump inspectors are looking for evidence of tampering with readers at fuel pumps. When and if our inspectors find a skimmer, they immediately contact law enforcement. In the past, inspectors were not checking for skimmers, but as the threat of skimming increased, we incorporated an additional inspection into our responsibilities at the KDA without an additional cost to the taxpayer.”