A crackdown on organized crime by Bulgarian law enforcement in May resulted in the seizure of more than 200,000 bitcoins - an amount worth more than $3 billion at today's bitcoin prices and enough to pay one-fifth of the country's national debt.

According to a press release dated May 19 from the Southeast European Law Enforcement Center (SELEC), a regional organization of 12 member states, including Bulgaria, 213,519 bitcoins were seized that month. Twenty-three Bulgarian nationals were arrested in the operation and officials said at the time that the arrests and subsequent asset seizures followed an investigation into an alleged customs fraud scam through a virus infiltrated in the Customs Agency's computerized systems allowing the perpetrators to skip paying fees when transporting goods into the country. The virus was uploaded to government machines by bribed agents, according to the release.

The release also noted that the offenders choose bitcoin to invest and save the money because it is rather difficult to track and follow.

At the time of writing, the amount seized is worth approximately $3.5 billion, at a price of roughly $16,492. The current value of $3.5 billion is reported to be enough to pay approximately 20 percent of the country's debt. Meanwhile, the country's gross domestic product in 2016 was $52.4 billion.

What remains unclear at this time is what the Bulgarian government is doing with the seized bitcoins.

Bulgarian media have reported that the head of the Special Prosecutor's Office, Ivan Geshev, "said on Dec. 8 that the Prosecutor's Office and the Interior Ministry had not seized bitcoins." Geshev reportedly attributed the claim that Bulgarian authorities had seized the bitcoins to SELEC.

Bitcoin is a virtual currency that emerged in the aftermath of the 2008 financial crisis.

It can be bought and sold using regular cash, but the actual coins exist only in cyberspace in the form of a numerical code.

Once purchased, they can be exchanged for some goods and services like normal money or transferred into other currencies.

Unlike money issued by banks and heavily regulated by governments, bitcoins are untraceable and can be exchanged anonymously with anyone in the world with the click of a mouse. Conventional online payment methods such as bank transfers and PayPal go through banks, which insist on customers disclosing their identity. But bitcoins can be bought for cash through ATMs with no questions asked. Yesterday, bitcoin surged past $18,000 after making its debut on a major global exchange, but was trading lower, highlighting the volatility of the controversial digital currency that has some investors excited but others nervous.

Trading on a futures contract began at 6 p.m. on the Chicago Board Options Exchange (Cboe) at a price of $15,000.

Heavy traffic made the Cboe website inaccessible for the first 20 minutes, but it said: "Trading runs on very separate systems and was totally unaffected by the website issues." Around 10 GMT yesterday, bitcoin was trading at $17,600 per unit for the futures contract expiring on Jan. 17, after reaching a high of $18,850, according to the Cboe website, meaning it exceeded the highest value reached on alternative non-regulated internet platforms.