DALLAS -- Sophisticated credit card skimming devices have found inside gas pumps three times in just over a couple of weeks, authorities say.

It’s a new twist on an old problem. These devices were so sophisticated that credit card numbers can be downloaded remotely.

“They’re taking steps to make sure there’s no fingerprints on the deal by shrink wrapping,” said Lt. Tony Crawford, commander of the financial crimes unit. “They’re sophisticated. They know what they’re doing.”

The first devices were found July 19 at an Exxon gas station at 15707 Hillcrest Road. Two illegal credit card scanning devices were discovered attached to the hardware inside two separate gas pumps. The devices were attached to the internal wiring of the machine.

Customers had been complaining that the pumps had been freezing up so a technician had been called, and that’s when the devices were found.

Candi Judd says she comes to the station on Hillcrest all the time.

She says she looked inside the credit card slot to see if anything appeared out of the ordinary.

Judd was surprised when she learned that she wouldn’t actually see anything since the skimming devices are installed inside the pumps.

‘It's scary,” she said.

Judd says her family always gets gas here.

She says her son recently had a bunch of fraudulent charges on his debit card. It's got her wondering if that's how thieves got his card number.

“There were hundreds of dollars taken out of his account,” she said.

On July 24, a device was found at an Exxon gas station on 7650 Campbell Road. It was wired directly into the gas pump circuit board.

On Monday, scanning devices were found inside three pumps at a 7-Eleven convenience store on 15050 Preston Road.

Police have no suspects, and they have no idea how long the devices were inside the pumps.

Turns out it’s actually pretty easy to access gas pumps, authorities say.

For convenience, there’s only a limited number of unique keys that can access pumps. That means if you have just one of those unique keys, you can access thousands of pumps.

The Secret Service estimates that skimming costs consumers more than $3 billion each year.