Four people were arrested Thursday in Quebec as police executed warrants in two communities north of Montreal as well as in the Toronto area.
Four other suspects from Ontario remained on the lam, actively sought by police.
Police demonstrated during a news conference on Thursday just how easily the fraud was perpetrated.
The ATMs were usually rigged in broad daylight as people conducted their banking business.
Police said the accused installed card cloning equipment in more than 200 ATM machines in Quebec and Ontario over the years, with cameras hidden in the rigged ATMs to capture pin numbers.
The fraud network members had to come by every two hours — the lifespan of the batteries and illicit gear being used — to collect the equipment and card data.
Police said their investigation had been going on for a few months, but the fraudulent activities began in 2008.
Among those arrested was the alleged leader of the network, Martin Antonov Kuzov, 52.
Some of the ATMs were affiliated with bank branches located in the Montreal area, a police spokesman said.
"Fraudsters, then in possession of the pin and card numbers, transferred this information abroad where large cash withdrawals were made," said Benoit Richard, a Quebec provincial police spokesman.
Richard said the majority of those who had their bank accounts compromised were from Quebec.
The information being gleaned was used to make withdrawals abroad, particularly in places where the safer chip technology is not yet prevalent such as Mexico and Asia.
"These fraudsters caused significant financial losses to the victims, in addition to large sums of money that was used in funding other criminal activities," Richard said.
Police executed search warrants in St-Sauveur and Piedmont, two communities located in the lower Laurentians region north of Montreal.
All the accused are Canadian citizens of Bulgarian origin, police said.
Three others arrested in Quebec are Vassilina Dimitrova, 48; Borislav Petrov, 53, and Iren Vasilev Atanasov, 42. They were to appear in court in St-Jerome on charges of fraud, possession and trafficking of personal data as well as possession of cloning instruments.
The four people still being sought are Konstantin Sirakov, 39 and Stefan Stefanov, 45, of Toronto. Two other men, Vencislav Gigov, 53, and Valentin Borisov, 51, are from North York.
Quebec provincial police said they had the help of provincial police in Ontario for Thursday's operation.