NASHVILLE, Tenn. -- Metro police said there's been a rash of ATM skimming, and they believe there are more than 300 victims.

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Skimming is when thieves place a piece of equipment over the ATM card slot. The device copies all of a user's information so thieves can then clone the card.

There have been 39 reports just in the last week.

Police said ATMs across Nashville have been hit, including machines in Brentwood and Belle Meade.

The thieves, who travel in groups, have gotten away with $23,000.

"The suspects take the data and clone a card with it and put your data on the back of a gift card," said Metro police Lt. Mickey Garner. "If you go to the ATM and there's something attached to the machine that looks suspicious, don't use that machine; go somewhere else."

Police recommend that customers keep checking their bank accounts for suspicious activity and that they not put their cards inside an ATM if something is attached on the outside.

"I would tell everybody to always check your account -- never go days and days without checking it," said Amy Hayes, who said she lost $1,214 after swiping her card through a skimmer.