A woman has admitted using false documents to get mortgages for low-income families who wouldn't otherwise be able to get them.
The fraud, relating to 10 property transactions in 2010, is worth $3.9 million.
Ramni Kumar has pleaded guilty in the Auckland District Court to 10 charges of dishonestly using a document.
She bought properties at low cost and bumped up the price before selling them to someone else.
The Serious Fraud Office says Kumar used false documents so the end purchaser could get a mortgage.
It says it still has concerns about what could be further cases of mortgage fraud in the current market.
SFO director Julie Read says vulnerable buyers can be exploited in a market which has a high property demand and rapidly rising prices.