MADISON, Wis. -

When police arrested two men suspected of placing a skimming device on a gas pump in Brookfield, one of the men dropped a set of keys that would open the pump. 

That key is one of the vulnerabilities criminals have found that make gas pumps an easy target.

“A lot of the keys and equipment skimming devices you can simply purchase online,” said Brayton Grinnell, a crime analyst with the Madison Police Department.

Unless a gas station owner changes the locks on their gas pumps, a universal key will open it. Armed with that universal key and the skimming device, it doesn’t take long for it to be put on the pump.

“It is a very simple practice, actually. From what we’ve been seeing, it take about a minute to unlock the terminal and put the device on and they’re gone,” Grinnell said.

In recent weeks, at least 15 skimming devices have been found on gas station pumps in southern Wisconsin. Investigators do not believe the people placing the skimming devices on gas pumps are acting alone.

“Based on some of the intelligence that our department has seen and collected over the year, I would definitely say it is organized,” Grinnell said.

To deal with the problem, Madison police will be meeting with area gas station owners. They will be recommending that gas pumps be inspected at least once a day to look for skimming devices.

As for consumers, they recommend using pumps located closer to the station that can be seen by employees. They also suggest keeping a close eye on credit card activity.

“Best advice that I can give is checking your credit card statements more often than you normally have in the past, daily if possible,” Grinnell said.