A look at the collapse of Zondacrypto, Eastern and Central Europe's biggest crypto exchange, which went dark in April and is facing money laundering allegations (Andrew Higgins/New York Times)

Zondacrypto, the largest cryptocurrency exchange in Eastern and Central Europe, ceased operations in April after its platform went offline. Regulators have opened investigations into the firm for alleged money-laundering activities, and authorities are seeking to trace missing user funds. The collapse has left thousands of customers without access to their assets.