The Serious Fraud Office says the Christchurch rebuild has the potential to generate $1 billion of fraudulent activity.
Acting chief executive Simon McArley told Parliament's Law and Order select committee on Wednesday that it has been looking at what has happened internationally with fraud related to recovery from natural disasters.
He said a Deloitte report estimates there is a 7% to 15% chance of fraud in any disaster recovery.
With a $30 billion price tag on the rebuilding of Christchurch, Mr McArley says there is a potential loss of $1 billion to fraud relating to procurement, construction, investment and claims.
Mr McArley says the SFO is already investigating two or three potential fraud cases involving insurance and procurement fraud.