The organisation, which comprises 12 member states, said at the time: "The offenders choose the Bitcoin way of investing/saving the money, because it is rather difficult to be tracked and followed."
The virtual currency is made up of lines of computer code which are digitally signed each time they travel from one owner to the next.
Transactions can be made anonymously, making the currency popular with libertarians as well as tech enthusiasts, speculators - and criminals.
Originally the currency was worth just $1 per unit - although this has surged to an all-time high of more than $16,600 amid violent market swings this month.
Tech-savvy users called "miners" use their computers to make complex calculations in a bid to verify that a 'block' of Bitcoin transactions are genuine.
It is similar to cracking a code - and it takes more than 1.7billion attempts each time using an enormous amount of computing power as well as electricity.
Users often combine their processors virtually to work together completing millions of calculations per minute between them.
In reward for their efforts, the miners who crack each code are rewarded with a share of the currency in the form of 12.5 newly created Bitcoins.
But for the average person, the costs involved with mining are so high that it is no longer worth getting involved.