 Fremont County authorities are advising residents of card skimmers located on multiple pumps at Casey's in Hamburg. The Fremont County Sheriff's Office's credit or debit card skimmers were located on pumps 3, 4, and 5 at the Casey's in Hamburg at around 3 p.m. Thursday. Authorities say the skimmers have been on the pumps for an unknown amount of time. The Sheriff's Office urges residents with those three pumps who have used those three pumps recently to check for any fraudulent activity on their bank accounts.