Allied Farmers, which bought the assets of Hanover and United Finance, admitted it had initiated regulators' inquiries into Hanover behaviour.
SFO chief executive Adam Feeley said accordingly, the probe had been evaluated to a "Part II" investigation under the Serious Fraud Office Act.
"Given the intense public interest and media speculation, it has not been appropriate to make any public comment on this matter until we had a detailed understanding of the issues involved, and the entities and individuals behind the Hanover operation.
"We have undertaken extensive preparatory work and are now in a position to move into a more active phase of the investigation," he said.
The news that the inquiry was under way and that Allied had had a role in initiating it, could take some of the heat out of the Allied Farmers annual meeting today.
The directors will front up to shareholders in the company's first annual meeting since undertaking the debt for equity swap deal with Hanover last December.
It was not certain yesterday how many investors would make the trip to the company's home town of Hawera.
The company said it had considered holding the meeting in Auckland but had settled on keeping it in Hawera because that was still where the largest number of its shareholders were based.
Managing director Rob Alloway said the company was "quite shocked" at some of the activity that took place before its acquisition of the Hanover and United assets and immediately moved to alert regulators.
Allied staff had provided relevant files and interviews to both the Securities Commission and the Serious Fraud Office over the course of the year.
"We feel the actions of the Hanover board and management while under moratorium have had a significant impact on the value of the assets, and investors deserve to have this investigated."
Allied was surprised last Friday by Hanover asserting it would pursue the payment of the $5 million Allied refused to pay on the basis of "serious breaches".
The breaches included a failure to comply with an obligation not to enter into abnormal transactions that would adversely affect the value of the assets, Mr Alloway said.
Those actions included the releases of personal guarantees and the sale of assets at less than market value.
"Personally, I am aghast that they would have the gall to effectively ask ex-Hanover and United debenture holders for another $5 million, given what we now know about the Hanover lending practices and assets."
Allied believed it had further substantial personal claims against former directors and officers of Hanover, including claims arising from breaches of duties.
Those claims would be pursued, Mr Alloway said.
Mr Feeley said the scale of the Hanover collapse was such that it was not feasible for the SFO to investigate all aspects of its failure.
"We are focusing on some very particular transactions, and specific individuals within Hanover management and their board."
Having considered the Securities Commission report and several complaints, including Allied Farmers, it was decided the efforts of the SFO investigation were best focused on key areas relating to the payment of dividends and other transactions immediately before the announcement of the moratorium proposal, and debt restructuring involving the transfer of assets to Allied Farmers.
