The case centres on Mostrey Worldwide Services, which once held a quasi-monopoly on diamond delivery, but which was closed down by authorities in 2005 after a courier was stopped with a huge sum of cash.

Investigation suggested the company was using the free trade zone in Geneva, which is intended to simplify customs restrictions, to smuggle diamonds and escape tax. Swiss authorities cooperated and turned over more than 35,000 seized Mostrey shipping dossiers, which showed that diamonds supposedly for export were instead rerouted to Antwerp to be sold on the black market.
Since then, raids have been carried out on the offices and homes of dealers, including one incident in December 2006 when a diamond executive, Nikhil Manilal, collapsed and died in front of police when a warrant was being executed.

The Mostrey investigation also led to protests from diamond industry representatives after police seized about €63.5 million worth of diamonds as evidence, leaving many traders unable to do business. In 2010 a number of members of parliament proposed a new law
that would enable traders involved in cases of seizures to appeal and allow the facts of the case to be considered by diamond trade experts to ensure seizures were justified. That proposal, however, was rejected by the Council of State.

The 220 suspects have been identified from four fraud circuits used by Mostrey to launder money and avoid tax. One of the most notable is Dilip Mehta, CEO of one of the world's largest diamond companies, Rosy Blue, which has annual sales of about €1.2 billion. Mumbai-born Mehta, who was made a baron by the king in 2006, has denied any wrongdoing.

The 107 parties that form part of the first phase of the prosecution include 11 executives of Mostrey and the 36 companies who made the most use of the fraud system or against whom there is the most evidence. The worst offender is suspected of fraud worth more than €55 million, and the total fraud package could be worth more than €800 million.

The Antwerp World Diamond Centre (AWDC), which represents the sector, said it had already taken steps to combat fraud since the Mostrey case first came to light, including tightening controls and making trade more transparent.

Antwerp accounts for 80% of the world's trade in rough diamonds, 50% of trade in polished stones and represents 5% of all Belgian exports. The industry is responsible for the employment, directly and indirectly, of about 34,000 people in the city.

Meanwhile last week the Antwerp city council announced it had won a contest to host a new International Training Center on Corporate Opportunities, organised by the United Nations to do trainings in commercially responsible enterprise in the diamond trade. Antwerp beat competition from Tel Aviv, Mumbai and New York.