In an anti-corruption purge back in May, Bulgarian authorities seized 213,519 Bitcoins, at the time worth $500 million. Now their value is a staggering $3.6 billion.
This amount is enough to pay off a fifth of the country's national debt of $16.5 billion.
The operation involved a large-scale hunt for more than 100 addresses, suspects and vehicles. Out of the 23 Bulgarian suspects arrested, five were customs officers.
Bulgarian authorities seized equipment, devices for communication, computers, tablets and bank documents. At the time the offenders said they chose Bitcoin as a way of investing and saving money because it is rather difficult to be tracked and followed.
The transactions can be made anonymously, making the currency popular with criminals.
Bitcoin has seen an exponential rise in value this year, from just below $1,000 at the beginning of the year to over $18,000 on December 7.