Alexander Vinnik, one of the operators behind the former BTC-e crypto exchange, pleaded guilty to a charge of conspiring to commit money laundering on Friday, the U.S. Department of Justice announced.

Vinnik was an operator of BTC-e between 2011 and 2017, the DOJ said, and the exchange processed more than 1 million users transacting over $9 billion in crypto during that time.

BTC-e was linked to the hack of now-defunct crypto exchange Mt. Gox after it was used to launder some 300,000 (BTC) from Mt. Gox. BTC-e was shut down in July 2017, at the same time Vinnik was first arrested.

While Vinnik was arrested in Greece, he faced a lengthy extradition process, with U.S. and Russian and French authorities trying to convince Greece to send him to their respective nations. France did secure Vinnik's extradition and sentenced him to five years in prison, before Vinnik was sent back to Greece before eventually being extradited to the U.S. He initially denied he was an operator of BTC-e, saying he was only an employee at the exchange.

BTC-e did not register as a money services business in the U.S., did not operate any know-your-customer or anti-money laundering rules and did not collect any customer data, the DOJ said Friday. Vinnik did use shell companies to process fiat conversions for BTC-e, the DOJ added.

The press release said the exchange did receive funds from criminal activities including ransomware attacks, hacks and other schemes, and Vinnik was directly responsible for some $121 million in losses.

In a statement, Deputy Attorney General Lisa Monaco said, "Today’s result shows how the Justice Department, working with international partners, reaches across the globe to combat cryptocrime. This guilty plea reflects the Department’s ongoing commitment to use all tools to fight money laundering, police crypto markets, and recover restitution for victims."