French, Belgian and Israeli investigators have brought down a scheme that defrauded €6 million ($6.64 million) from French and Belgian citizens, a Jan 29. press release from Europol reads.

The fraudsters promised significant returns for the victims’ investment in what appears to have been a Ponzi scheme.

The international network of fraudsters was allegedly masterminded by a French-Israeli citizen. Authorities arrested nine suspects connected with the scam in 2019.

The investigation started in 2018 and was coordinated by Europol and Eurojust.

The criminals reportedly set up a system promising large gains from investments in Bitcoin, diamonds and gold, and offered their “services” on undisclosed online platforms.

The fraud displays the tell-tale signs of a Ponzi scheme. The organizers promised returns from 5 to 35 percent then pretended to manage users’ wallets and invited them to invest more money. Some of the victims were indeed paid interest to increase their confidence in the platform.

Organizations were also targeted, with a “big French private company” and a local French authority reportedly falling victim to the scam.

Fraudsters succeeded in collecting at least €6 million, with outstanding invoices for several million more. Authorities managed to recover more than one million euros, with the rest supposedly having been transferred outside of the European Union.

French regulators previously noted a significant increase in crypto-related scam threats in the country.