Brazil's largest crypto exchange detected a breach in one of its systems early on November 2 and froze all deposits and withdrawals. A day later, Mercado Bitcoin said customers will not bear the cost of the hack and that client balances remain recorded in their accounts.

The exchange puts the assets involved at about $38 million and says $11 million has already been blocked with help from Tether, Circle, Paxos, BRL1 and Chainalysis. Outside estimates run higher: Hypernative flagged more than $40 million in suspicious transfers across at least 10 blockchains, Arkham traced at least $46 million and Chainalysis about $49 million. Tether separately froze more than $4.5 million in USDT tied to the incident.

Deposits and withdrawals remain suspended with no restart date, and the exchange has not disclosed how the attackers got in.

The incident follows the $6 billion Binance theft on October 29 that the FBI attributed to North Korea's TraderTraitor group. Mercado Bitcoin has not linked the two attacks. Like Binance, it has promised to absorb the losses itself, though neither pledge can be verified from the outside.