Interpol is still trying to find a couple of cashed-up Kiwis, believed to be living it up in Asia, after they were mistakenly given $8 million ($NZ10 million) by Westpac.

Rotorua service station owners Leo Gao and his girlfriend Cara Young fled New Zealand with about $NZ3 million after they discovered the money in their bank account.

But their chances of being caught have increased after they were joined overseas by Ms Young's sister, Aroha Hurring, who posted details about their location on her Facebook page.

Police believe the trio are in China after Ms Hurring foolishly updated her status to say she was drinking the local Asian beer and enjoying the heat.

Her mother Sue Hurring, who runs a hairdressing salon in Blenheim, has been helping police with their inquiries.

"Well, you've got to have a laugh," she said. "It is bizarre.

"She's never pinched a thing in her life. Probably as a little girl, yes, but so honest."

Ms Hurring says she blames her daughter's boyfriend.

"Well, if you really want to know I'd like to wring his blinging neck for getting the whole... I don't know what to say.

"Never mind Leo, he can stay there. Just come home now please [Cara]. It's going to be OK."

But getting the trio home could prove tricky, because New Zealand does not have an extradition treaty with China.

The affair began after the couple applied for a $10,000 loan to stop their business going under, but Westpac mistakenly transferred $NZ10 million into their account.

Westpac's New Zealand spokesman Craig Dowling says he had not banked on all the publicity the case has attracted, but is confident the accidental millionaires will be found.

"We're concentrating on making sure our people are OK with the attention this is getting, and then also following the money trail.

"The details of that we're still wanting to be a bit cagey about - we don't want to say anything that will jeopardise our chances of recovering the outstanding money."

Traumatised

He says a bank employee made a simple mistake.

"The entry in one area jumped from $100,000 to $10 million, so it was about a couple of errant noughts that caused a, quite a major issue."

The employee is reportedly so traumatised that they are now receiving counselling.

"It's probably pretty obvious to just about anyone that making a mistake that gets this amount of attention is not a pleasant thing to go through, and mistakes should not have led to this outcome," Mr Dowling said.

"There's a couple of other things that happened which make it a pretty unique event. It's absolutely a one-off for this, a keying error, to have gotten through to the stage that it did.

"We want to say we take responsibility for the checks that didn't work."