The cash had been withdrawn from at least 60 BNZ and Westpac accounts via a cash machine in Canada at the weekend. Other banks' customers, including the ASB's, have also been affected.
The latest cases have allegedly targeted eftpos terminals inside stores _ possibly by replacing them with machines with devices fitted or by tampering with them in store.
Detectives from the Auckland City District Financial Crime Unit are liaising with their Canadian counterparts regarding the four men.
The full extent of the offending has yet to be ascertained and detectives are working with the Financial Services Industry to ascertain the impact for New Zealand.
The scam is separate from one that targeted five ANZ and National Bank ATMs in Auckland in February and March, when more than $1 million was taken by fraudsters who withdrew the money in cities around the world.
In those cases, a "skimming'' device was fitted over the slot where the card was inserted into the ATM. Information was collected from the card's magnetic strip while a tiny camera fitted above the keypad recorded the PIN being entered.
