Brazil's largest cryptocurrency exchange has paused deposits and withdrawals following a security incident detected in the early hours, with on-chain monitors flagging roughly $40 million in suspicious transfers linked to Mercado Bitcoin. The company has not published an official loss figure.

Mercado Bitcoin said on Monday that it identified and halted a security incident overnight. According to the exchange, there were no client losses and no data leak. As a precautionary measure, it froze deposits and withdrawals, and staff are tracing assets while cooperating with authorities.

Brazilian financial outlet Exame reported that security firm Hypernative linked wallets associated with the exchange to more than $40 million in outflows — approximately R$217.7 million at the exchange rates then prevailing.

What Mercado Bitcoin Confirmed

In a statement on X, Mercado Bitcoin said its teams are investigating the case, tracking the affected assets, and working with authorities, adding that it will provide regular updates through its official channels.

A follow-up post published destination addresses associated with movements tied to the incident, noting that the list is intended for tracing purposes only. The addresses span five networks:

• EVM: 0xe485e7A70b1131216Cb47CA4555c4Bbb2C742478
• Bitcoin: 19qGpsHvzh1t6pVi526XNNkh6hW6prDZp
• Solana: 3YX6WHncP1Ra4AotE9YLawFt4nPmxyux288FWXkEW97J
• Stellar: GDXYRI6IONQA5YTGRLQ603FGJ2BWXPJTTQPUXFPSEXSRKBZLFKMZSOLP
• Tron: TEX3HuDRHRa3tnYpy96M4UfSx62VhDyA5L

The exchange said it is still working to restore service safely. Its status page showed trouble with login, the app, signup, and the Trade API that morning. Those service statuses, together with the exchange's official X account, are where customers can track whether the freeze on deposits and withdrawals is being lifted.

On-Chain Flags Behind the Mercado Bitcoin Hack

Hypernative's initial assessment, reported by Exame, pointed to large balances at addresses later mirrored by Mercado Bitcoin. The holdings included approximately 2,852 ETH and about 106 BTC, along with thousands of SOL, millions of XLM, and tokens on Avalanche, XDC, Tron, and more than 200 other assets. Because such figures come from tracing flows on public ledgers rather than from the company's own books, they stand as analyst estimates until the exchange confirms a number.

Public Bitcoin blockchain data corroborates part of the picture. The address 19qGpsHvzh1t6pVi526XNNkh6hW6prDZp shows about 106.07 BTC across seven transfers, and the coins were unspent at the time of checking on the public Bitcoin chain. A Solana view of the named destination showed about $1.5 million in tokens, led by USDT.

Exame also reported that Tether blocked nearly $3.7 million in USDT on addresses under investigation. As the issuer of USDT, Tether can immobilize tokens at specific addresses, and the freeze prevents further movement of those stablecoins — but it does not recover the rest of the mixed haul.

Chain snapshots alone do not prove that every flagged coin came from Mercado Bitcoin custody. They do, however, show why the company published the destination addresses and asked the market to monitor them.

Why the Freeze Matters

Brazil's biggest retail crypto venue has hit the classic exchange-heist sequence: an overnight scare, a deposit and withdrawal freeze, an assurance on client safety, and then destination wallets published for the chase. Freezing the rails is the standard opening move when an exchange suspects its keys or signing systems are compromised, because open withdrawal channels would let an attacker keep draining funds.

Users cannot move their funds while the rails remain shut, even if their balances appear intact. Regulators will expect a clear technical account once withdrawals resume, and issuers and platforms will be watching whether more flagged coins are frozen before they reach mixers or OTC desks.

The timing raises the stakes. The Mercado Bitcoin announcement landed days after a multi-billion-dollar hot-wallet drain elsewhere — a different scale, but the same lesson. When custody keys or signing infrastructure fail, the first move is to stop the bleed. Then the race to move funds across chains begins.

New rails change the surface of theft, but the custody problem remains old. Until Mercado Bitcoin reopens deposits and withdrawals and explains what failed, the $40 million figure remains an analyst estimate standing beside an official freeze.