Allied Farmers says it complained to the Serious Fraud Office about Hanover Finance shortly after it bought the failed finance company's assets and loanbook a year ago.
The SFO announced on Monday it has been investigating Hanover for the past three months and now has reasonable grounds to suspect fraud.
The rural services company says it will pursue further substantial claims against Hanover's directors and executives, including breaches of duties.
Hanover was owned by Mark Hotchin and Eric Watson and 16,000 investors had their investments frozen in July 2008.
In December 2009, the company's assets and loanbooks were sold to Allied Farmers for $400 million.
Allied Farmers' managing director Rob Alloway says he became aware of some of Hanover's activities before the purchase.
Mr Alloway told Checkpoint some of the assets were misrepresented or overvalued and supporting information by so-called professionals was particularly misleading.
"I think it's endemic in the tier 2 finance industry where there's been a number of sloppy procedures and things in place for monitoring these types of organisations."
Mr Alloway says there has been some changes to legislation which have tightened some areas of concern.
SFO chief executive Adam Feeley says his office will be interviewing a small group of key Hanover staff and professional advisers.