Finance ministry inspectors, police and the public prosecution department have seized more than €25m in crypto currencies in recent months in a string of separate investigations.

The currencies, mainly bitcoin and ethereum, are becoming increasingly popular ways to hide criminal cash, because they are both anonymous and can be moved around the world quickly.

Crypto currencies are widely used as a means of payment in various types of crime, both tech-related, and now more mainstream, such as drugs and human trafficking, fraud and tax evasion, the public prosecution department said.

The investigation also revealed that criminals are also dealing with unwanted exchange rate fluctuations by converting the crypto currency into so-called ‘stable coins’ such as USDT, which is linked to the US dollar.

Some of the people arrested come from the Netherlands, others have a foreign nationality and will be extradited to face charges at home, in line with international agreements.

Last year, a similar string of investigations netted €8m, the year before just €1m.