The Serious Fraud Office has confirmed a second round of investigations into the NZF Group Limited and NZF Money Ltd.
NZF Money was placed into receivership on last year on 22 July, owing debenture holders approximately $16.4 million.
The company, which provided commercial and residential loans, is under investigation from the SFO and Financial Markets Authority for alleged related party transactions between members of the group, its directors and officers.
The transactions cover a period from 2006 to the present.
Last July, the company was forced to pull its prospectus by the Financial Markets Authority, which raised concerns about its disclosures of asset quality and liquidity.
In a statement, SFO Chief Executive Adam Feeley said the organisation was conscious of the need to respond quickly.
"We are satisfied that there are valid grounds for an investigation into the wider group, and that there is a legitimate interest in publicly advising investors of this investigation."