The Serious Fraud Office is investigating transactions involving overstated property values on all types of property.
The SFO says a small number of valuers are undermining confidence in the profession and warns investors to beware of inflated property values.
It is investigating transactions in which it says property values have been significantly overstated - some by 500% over their market value.
The SFO has referred a number of transactions to the Valuers Registration Board and is considering charging one valuer with fraud.
Chief executive Adam Feeley says where valuers had a clear intention to deceive investors criminal charges will be laid, but often the SFO has been unable to establish fraud.
Property investors have been making bad decisions based on valuations that were inflated beyond what were commercially realistic, Mr Feeley says.
Mr Feeley told Checkpoint while some property values have been overstated by 500%, more problematic are those inflated by 30% or 40%.
"Those are the probably the valuations that most concern us - they are not valuations which scream fraud, but they are valuations which suggest one would have to seriously question the accuracy and quality of those valuations."
The Institute of Valuers says it is very concerned about overstated property values being investigated.
President Nicki Bilborough told Checkpoint the board's penalties are severe and range from a fine to deregistration.
