The Secret Service is warning Americans about to hit the road on the Fourth of July to be wary of being taken for a ride at the gas pump — where fraudsters are targeting their credit card information.

Scammers have been installing tiny devices inside the pumps called skimmers, which copy customers’ credit card data.

This past weekend, the Secret Service canvassed the nation in search of the devices — recovering 59 of them at 85 locations.

“So what happens is you go to your local gas station, you put in your payment card, you pump your gas and you drive home,” Matthew O’Neill, assistant to the special agent in charge of the Criminal Investigative Division, told ABC News.

“But what’s in reality happening is during that transmission process, a skimmer is acting in between where you put your card in and the point of sale terminal that’s transmitting the data to a financial institution and they’re stealing your payment card numbers.”

The swindlers gain access into the machines by buying commercial keys that can open the pumps online, according to the news outlet.

Once the criminals have a customer’s information, they can print fraudulent credit cards and use them to make purchases.

“They’re monetizing the stolen payment card data in multiple ways and the easiest way is they’ll take the stolen payment card number and will re-encode a gift card or credit card and then they will use that to buy electronics, gift cards, stuff that they can fence on gray market, the black market or the open market,” O’Neill told ABC News.

According to the Secret Service, millions of dollars are being swiped each year from credit card information pilfered at the pump.

“It will take just a matter of minutes depending on the level of tradecraft that the fraudster has,” O’Neill said.

A sophisticated skimmer can send credit card data through a Bluetooth device.

“With a Bluetooth skimmer you don’t ever have to retrieve the skimmer if you don’t want to because the data is being sent through the Bluetooth device to another internet-connected device,” he said.

To reduce the chance of being victimized, customers can pay with credit cards inside the gas station, rather than at the pump — but the safest way to pay is with good old cash.