The number of fraud complaints referred to police by the Earthquake Commission has doubled in the past five months.
An independent report to the commission on the fraud risk cites instances where contractors have given fraudulent invoices and customers have tried to claim for non-earthquake damage.
In March, the commission had referred 20 fraud complaints to police which resulted in four successful prosecutions.
Since then, it has referred another 20 cases, with some of those before the courts.
Commission chief executive Ian Simpson says the 40 fraud complaints are the result of about 1000 files being analysed, and mostly involve customers.
Mr Simpson says it's an ongoing problem, which is why the commission needs to keep its eyes peeled.
Commission customer services general manager Bruce Emson said files have been built up on people possibly involved in fraud and they have been handed to police, who may prosecute.
Mr Emson said staff are dealing with huge sums of money and human nature is such that if you put temptation in the way of people, somebody will stumble.
He said data is analysed to figure out behavioural trends and privacy laws have been adhered to.
Mr Emson said the incidents in question are under investigation and aren't before the courts yet.