MADISON, Wis. -

Criminals rigged more than a dozen gas station pumps in Wisconsin with a device to steal credit card information from customers, a state consumer protection group said.

The Wisconsin Department of Agriculture, Trade and Consumer Protection warned consumers Tuesday that 15 skimming devices were discovered at gas pumps in multiple counties over the last five weeks.

DATCP said it only takes a few seconds for a criminal to install a credit and debit card skimmers, which give thieves instant access to cardholders' financial information.

DATCP inspectors have documented from Aug. 5 through Sept. 9 that internal devices were discovered inside gas pumps.

DATCP advised consumers who pay at the pump to keep a close eye on their card statements and on the pumps they use to fill their vehicles.

Skimmers can be installed externally over the card reader, or internally, which the DATCP warning said typically includes a cable with an inline recording device that is run between the card reader and main board.

"A consumer may likely have no indication that they used an altered dispenser until they find a discrepancy on their bank statements," Division Administrator of Trade and Consumer Protection Frank Frassetto said.

While at the pump, consumers can protect themselves by lightly wiggling the card reader on the pump, DATCP said. External skimmers may feel loose and come off. One can also spot if the security seals have been broken on the dispenser cabinet. Other signs of tampering include visible tool marks or loose card readers. Anyone who spots something suspicious should tell the store manager and not use the pump.

Shoppers should also pay close attention to their monthly statements and regularly check credit reports to identify if there is any fraudulent activity, Frassetto said.