Bitzlato, the little-known crypto exchange that last week was charged by the U.S. with money laundering, exchanged around 1 billion euros ($1.08 billion) in assets linked to criminal activities, European Union police agency Europol said in a statement Monday.

The company's CEO, financial director and market director were all arrested in Spain, as well as one additional individual in Cyprus and one in the U.S., Europol said, after the U.S. Department of Justice announced it had shut down the Hong Kong platform and taken founder Anatoly Legkodymov into custody in Miami.

On Jan. 18, the U.S. Treasury's Financial Crimes Enforcement Network (FinCEN) formally labeled the company a “primary money-laundering concern,” a serious designation which usually cuts off a business off from the global financial system.

The crime-linked assets represented about 46% of the 2.1 billion euros ($2.3 billion) received by the platform, Europol said.