Fairfax County police are investigating skimmers that were found attached to two automated teller machines at Fairfax hospitals. The devices, discovered this week, are designed to copy personal bank card information and pass codes for thieves.

Authorities said the devices may have been in place for weeks. They are urging people who may have used the machines to check their financial statements.

Skimmer found on hospital ATM (Courtesy of Fairfax County Police)

Police said that in one case, a hospital employee found the skimmer when she tried to insert her ATM card and the device fell off the machine. Police said a hospital security guard found the other skimmer.

The ATM at the cardiac-care facility was also targeted by a skimmer device in August and September, authorities said.

In that case, police said thousands of customers may have had their personal information stolen. Police said people who had used the ATM during that period reported fraudulent purchases for groceries, expensive coffee and cash withdrawals from other machines.