DENVER -- A Denver woman said she might be Colorado's first victim of an ATM scam called "skimming," where an extra card reader is attached to an ATM.

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See How ATM Skimming Scam Fraud Works

Naomi Jiminez said someone stole $900 from her account and she suspects it's because of an illegal card reader.

In the scam, the ATM works as it should but the "skimmer" device, which looks just like a regular card reader, stores your name and account number, which can then be downloaded onto the Internet to make a duplicate card and then access your account.

"At the same time I'm at home, somebody is over on South Broadway pulling out $900 of my money. I have no other explanation for it," Jiminez said.

Jiminez's bank is looking into her case to see if she'll get her money back. Colorado authorities said they know about the skimming scams but don't have any "confirmed" cases in the state so far.

Authorities in other states said that most of the times, these false card readers are on ATMs that are placed in convenience stores.

Skimmers are also attached to the outside of the gas pumps. Officials say be on alert and keep a close tab on your bank and credit card statements.