ANZ says it is not contacting customers from other banks affected after fraudsters tampered with its cash machines.
On Thursday, the bank confirmed that that money had been transferred from a small number of accounts into Bulgarian bank accounts.
It said the fraudsters appear to have placed devices on ATM machines in Auckland for only a few hours before the bank's security programmes detected the fraud.
ANZ managing director of retail Kerri Thompson believed those responsible timed the crime around the public holiday on Good Friday to get as many victims as possible before the bank noticed.
The bank would not disclose how many people have been affected, how much money was taken or when.
Spokesperson Stefan Herrick said on Friday ANZ was contacting its customers affected but could not track customers from other banks who might have been defrauded.
Mr Herrick says anyone who notices unusual transactions on their accounts should contact their bank.
ANZ is reimbursing its customers and issuing new cards, and other banks will do the same for theirs, he says.