WASHINGTON — Detectives are warning people to be extra vigilant while pulling money out ATMs this time of year: A new type of ATM skimmer popping up across the area is undetectable.

“There are various types of ATM skimming devices out there. This is a typical one,” said forensic scientist Brianna Hahn. Inside D.C.’s Digitial Evidence lab, Hahn holds a bright green piece of plastic with a slot for a credit card.

But the type-overlay skimmers, which consumers could attempt to jiggle or pull off to check if they were present on an ATM, are old technology for crooks. Now some have what are called deep insert skimmers.

“It goes inside the reader part where you insert your card, so you don’t even know it’s there. So it’s just placed inside the ATM,” Hahn said.

The piece, which is hidden where someone would insert their card into an ATM, uses an SD card to capture the card numbers. But it works best for the thief, Hahn said, if it’s accompanied by a camera which is also installed where the user can’t see it.

“So what happens is when your credit card number is being skimmed, the video is recording the pin number. So they match the card number to the pin number at the same time of the transaction,” Hahn explains.

The technology has been found by detectives in D.C. and in Montgomery County.