The stolen account information was used to make withdrawals at ATMs in Reno and Sparks, Nev.
"People really need to be vigilant," Boise Police Chief Jim Tibbs said at a May 19 news conference. "If anything looks unusual (at the ATM), they really need to report it right away."
Police said the skimmer is difficult to recognize because it is small and may appear to be part of the ATM. According to victim descriptions, the one on the machine they used was just a little larger than the card itself.
Some victims came forward when they learned of unauthorized withdrawals from their accounts. Police became convinced it was a skimming device after interviewing them.
Most of the Boise victims recorded losses of $4,000 to $5,000, with some as high as $12,000.
There are no suspects in the case, according to the Idaho Press report.
Tibbs said it is not known if thieves targeted other ATMs in the area. Skimmers are most often used at busier ATMs and on weekends, police said, when bank employees are usually gone.
Lynn Hightower, communications director for the Boise Police Department, said police were investigating a similar scam at a second ATM that involved fewer victims.
