MADISON, Wis. (AP) — Consumer protection officials have issued a warning about card skimmers that have shown up at gas pumps across Wisconsin.

Thieves that have attached the skimmers at the pumps are stealing credit or debit card information. The Department of Agriculture, Trade and Consumer Protection says state investigators found at least 15 skimmers during inspections of gas pumps over the past five weeks.

The devices were found at stations in Edgerton, Janesville, Milton, Random Lake, Camp Douglas, Madison, Lake Delton, Franklin, Brookfield, Appleton and Oshkosh.

The illicit skimmers operate two ways. An external skimmer is placed over the real card reader. An internal skimmer has a recording device and cable that connects with the main board.

The FBI and IRS are also conducting skimming investigations at gas stations, but haven't announced any results.