Placer County sheriff's investigators are warning the public to always stay aware while pumping gas at any area gas station.

An uptick in the discovery of cannibalized cell phone parts used to "skim" credit card data prompted the sheriff's department warning.

The gear can receive real-time transactions of credit card data from just about anywhere, sheriff’s officials said, and never need to return to the scene of the crime.

The states most heavily impacted by skimmers are California, Arizona and Florida, according to investigators.

Investigators said there aren’t typically any outward signs that a gas pump has been compromised by a skimmer. Further, the scammers tend to target older pumps, stations next to major highways and stations that lack security cameras.

To avoid having your credit card skimmed, go to gas stations that appear to place an emphasis on physical security, investigators said.

Also, avoid using debit cards, because some devices can detect PIN numbers. Instead, use cash or pay with your card inside the gas station. Exxon Mobil has an application you can install on your phone to pay for gas.