The US Justice Department said the bitcoin was hacked by 'Individual X' from Silk Road

The US has seized more than $1 billion worth of bitcoin connected to the Silk Road criminal syndicate, the Justice Department announced Thursday.

The funds were taken by on Tuesday after being traced to a bitcoin address by an unnamed "Individual X," according to a US Department of Justice press release.

"It was further determined that Individual X had hacked the funds from Silk Road," the DOJ said.

The DOJ said it filed a that the funds are subject to forefeiture, adding that it expects to prove the case to the court.

"Silk Road was the most notorious online criminal marketplace of its day," said US Attorney Kelly Anderson of the Northern District of California.

"The successful prosecution of Silk Road's founder in 2015 left open a billion-dollar question. Where did the money go? Today's forfeiture complaint answers this open question at least in part. $1 billion of these criminal proceeds are now in the United States' possession."

In 2015, Ross Ulbricht was sentenced to life in prison after being convicted of masterminding the criminal website Silk Road, which sold $200 million in drugs to customers worldwide.

Ulbricht, who ran Silk Road under the alias "Dread Pirate Roberts" and was accused of commissioning five murders at a cost of $650,000, was sentenced to two life sentences for narcotics distribution and criminal enterprise.