Two New Zealanders whose bank mistakenly deposited $6.1 million dollars into their account took some of the money and ran, police said.

Authorities launched an international search for the couple, who operated a gas station in the northern city of Rotorua, and the Westpac Bank said Thursday it considered the money stolen.

The two applied to Westpac for a $6,000 overdraft, but 1,000 times that amount was paid into their account. The two then withdrew some of the money and disappeared, Detective Senior Sgt. David Harvey said.

Westpac conceded human error was responsible for making the couple accidental millionaires. Authorities did not release their identities.

Harvey said Interpol has been contacted for help, suggesting they may have fled abroad with the cash.

"We are currently conducting an investigation into the individuals that may have been involved in the withdrawal of that money," Harvey said.

Westpac spokesman Craig Dowling said the bank had recovered some of the money but declined to give further details.

The bank said in a statement it was "pursuing vigorous criminal and civil action to recover the sum of money stolen."

Banking Ombudsman Liz Brown said it is generally considered a criminal offense for people to spend money accidentally deposited into a bank account if they are aware that the cash is not theirs.

In her 15 years as ombudsman, Brown said she had been involved in 10 to 20 similar cases.