Police are looking at a Mobil gas station on Paseo Montalban in Rancho Penasquitos and a Shell station along Rancho Bernardo Road after several customers reported fraudulent charges on their credit and debit cards after filling up.According to authorities, a thief has been skimming or gathering card data and PIN codes during transactions. At the Shell station in Rancho Bernardo, the skimming device was inside the pump.The Shell station owners were the ones who discovered the skimming device. They told 10News they look for this type of activity every day. When they found the device last week, they said they immediately called the FBI."To me, it shows that the criminals are just getting more wily," said Amber Yoo, who is with Privacy Rights Clearinghouse.Yoo tracks data breaches across the nation. She said that often the charges are made out of state. One North County victim had a $500 charge at a Tennessee truck stop. But sometimes, the thief is closer than some may think."Like it or not, often times it is an inside job," said Yoo.Yoo recommends drivers use cash, a credit card or choose the credit function when using a debit card.