The alleged $30 million gaming machine fraud is understood to include a person who received substantial ''finder's fees''.
The Department of Internal Affairs confirmed summons have been served on four people on charges of obtaining by deception.
The men have been named as Mike O'Brien and his father Patrick, both of Blenheim, Paul Max, of Nelson, and an unnamed former gambling inspector.
The men face 20 charges between them and are due to appear in a Wellington court on February 2.
Mike O'Brien declined to comment when contacted yesterday. He has said the charges would be vigorously defended and Patrick O'Brien has said he had nothing to hide. Max has said, also, he would be defending the charges.
The three named men were connected with Bluegrass Trust, one of several trusts alongside New Zealand Community Trust and Infinity Foundation investigated as part of Operation Chestnut, by the Serious Fraud Office, Internal Affairs and New Zealand police.
It has been alleged one person approached racing clubs to fund the buying of bars, which in turn were aligned to ''race friendly'' trusts who returned money into the industry.
Bluegrass was established to fund the racing industry but was shut down. In 2012, the ODT reported Bluegrass Trust was the biggest pokie funder of the southern racing industry, despite having no venues in Otago and Southland.
