Customers from a Shoreview credit union and other financial institutions have had tens of thousands of dollars stolen by criminals who have used skimmers installed on ATMs to collect information and commit fraud, the Ramsey County Sheriff’s Office said.

“It’s serious,” said Sgt. John Eastham. “There have been several victims and these people — predators — are preying on hardworking people.”

Law enforcement know of at least two people who have installed the devices that can be attached to credit card readers to collect and transmit a customer’s credit and debit card data to criminals, who sell or use fake cards with the stolen information to gain access to accounts.

Sheriff’s deputies were tipped off to the criminal activity Sept. 23 when a skimming device was discovered at the City County Credit Union in Shoreview. A surveillance image shows a woman wearing a black dress standing in front of an ATM. Another image shows her with a man inside a red Ford Windstar.

Another image from the next day shows the man wearing a skull mask to conceal his identity as he reaches for a machine while sitting in a red minivan.

It is not clear how many of the devices the crooks have planted, but Eastham said they were discovered between Sept. 23 and 29. He also said Ramsey County was working with two law enforcement agencies in Dakota County where the pair also are suspects.

Losses have totaled “tens of thousands of dollars,” Eastham said.

Eastham said it is possible the suspects are not from the metro area.

Customers are encouraged to use ATMs inside financial institutions to protect themselves, but those who use drive-ups or walk-ups should visually inspect the machine before inserting their cards, Eastham said. He said customers should look that the opening where cards are inserted is flush and that nothing is sticking out. If something looks amiss, customers should call police.

“Trust your gut,” Eastham said. “If it looks suspicious, don’t use the ATM and go inside the bank.”

He also said that ATM users should shield the keypad when typing PIN numbers as a precaution as cameras can record a customer’s finger movements.

Crimes like this are hard to solve, he said, but anybody who sees a skimmer or has information can call the sheriff’s office at 651-266-7320.

“If we can get a hold of one of the skimmers, we might have evidence that might help us solve the crimes,” he said.