Two people were victims of fraud while using ATMs at 35 Young Street and 55 Queen Street South in Tottenham, according to Ontario Provincial Police.
One person was taken for $1,600 at the Alliston branch while the victim in Tottenham lost $3,800.
According to investigators, police responded to the incidents at the CIBC locations between 2 and 3 p.m. on January 5.
"Video surveillance shows that the victims appear to be completing their transactions at an ATM, going to leave the premises, and are then called back by the suspect, at which time, they tell the victim that their transaction hasn't been completed and therefore they can't use the ATM," police said in a news release.
The suspect will attempt to demonstrate the problem to the victim by putting an unidentified card in the machine that shows an error, police added.
"The suspects then physically take the card out of the victim's hand and put it partially into the ATM, hitting cancel, and then hand back what they think is their card but in reality is someone else's, or possibly a fake card," according to the news release.
Police say the real card is then used to withdraw funds from the victim's bank account. In the case in Tottenham, the card was also used to purchase several prepaid credit cards at local retailers.
From surveillance video it also appears that the male removes one of the shields intended to help hide the PIN number, and then observes the PIN entry over the victim's shoulder
Investigators are seeking the public's help to identify three individuals who are believed to be involved in the thefts.
If you know these individuals, please call 1-888-310-1122 (reference number E250018227, E250018291). You can also provide information anonymously by contacting Crime Stoppers at 1-800-222-8477 (TIPS) or www.crimestopperssdm.com.