The Dutch public prosecution department has three cases pending involving money laundering and the virtual currency bitcoin, the Financieele Dagblad said on Tuesday.

It is currently legal to trade in bitcoins, which rose 128% in value last year to a high of €980. However, the currency, which is unregulated, is also popular with criminals, hence the public prosecutor’s crackdown, the FD said.

The first Dutch case will be heard on February 6 and involves a 24-year-old man from Amsterdam and 27-year-old from Utrecht. They are suspected of laundering some €2.4m using bitcoins.

The second case involves four Dutch nationals who are said to have set up an currency exchange office specialising in turning bitcoins into euros.

The third, code-named IJsberg, is part of an international investigation into a money laundering gang and is expected to go to court at the end of the year, the FD said.

According to Europol, some 40% of online transactions on the dark web, where drugs and weapons change hands, involve bitcoins.