$72 Million In Bitcoins Stolen From Hong Kong Exchange

A bitcoin exchange in Hong Kong has been hit by a major theft: Nearly 120,000 units of the digital currency were stolen.

At the time of the theft, that was worth about $72 million, Reuters reports. But the value of bitcoin has dropped by more than 20 percent since the news of the theft broke.

It's not clear who stole the bitcoin from the exchange platform Bitfinex or how they did it, the wire service reports.

The funds were taken from users' individual accounts, or "wallets." The amount of bitcoin involved is approximately 0.75 percent of all the currency in circulation, Reuters says.

Bitfinex has shut down its platform while the exchange cooperates with law enforcement to investigate "the causes and consequences" of the security breach, according to a blog post from the company.

"The security breach comes two months after Bitfinex was ordered to pay a $75,000 fine by the U.S. Commodity and Futures Trading Commission in part for offering illegal off-exchange financed commodity transactions in bitcoin and other digital currencies," Reuters reports.

The Bitfinex hack is "one of the largest thefts in bitcoin's short history," The Wall Street Journal says.

In 2014, the bitcoin economy was badly shaken by a theft at the Mt. Gox exchange in Tokyo. About 850,000 bitcoin were stolen — nearly half a billion dollars at the exchange rate at the time.

And this June, a separate virtual currency — ethereum — saw a theft of about $60 million, the Journal reports.