Thunder Bay Police say 77 separate reports have been received about fraudulent activity affecting bank and credit union customers in the city.
Police suspect the thieves used altered electronic equipment to obtain debit card information. After the information was taken, money was then withdrawn from the accounts at ATMs in New York City.
Thunder Bay police said it's likely a compromised banking device was installed somewhere in Thunder Bay over the past year.
They said fraudsters typically hold onto the information for several months, and then use it all at once to make withdrawals in a large city.