Japanese crypto exchange DMM Bitcoin is warning that 4,502.9 Bitcoin (BTC), or approximately $308 million (48.2 billion yen), has been stolen from one of its wallets today, making it the most significant cryptocurrency heist of 2024.

“At approximately 1:26 p.m. on Friday, May 31, 2024, we detected an unauthorized leak of Bitcoin (BTC) from our wallet,” DMM Bitcoin told customers.

“We are still investigating the details of the damage, but the following is what we know at this stage. We have already taken measures to prevent the unauthorized leak, but we have also implemented restrictions on the use of some services to ensure additional safety.”

While the company investigates the theft, it has restricted numerous services on its platform, including registering new accounts, cryptocurrency withdrawals, buying on spot trades, and new open positions for leveraged trading.

DMM Bitcoin has not provided any information on how the theft occurred, but similar thefts were conducted in the past by gaining access to corporate systems or by exploiting flaws in smart contracts or websites. 

The exchange apologized to customers, stating that all Bitcoin (BTC) deposits will be fully guaranteed as they replenish the equivalent amount through the help of the group’s companies.

Cryptocurrency intelligence firm Elliptic, who is tracking the stolen Bitcoin, says that the threat actors have already split the stolen Bitcoin into multiple new wallets. 

This is likely done to obfuscate its tracks and evade blocks by other crypto exchanges if the threat actors attempt to exchange it for other cryptocurrencies.

Elliptic says that if this is confirmed to be a theft, it is the eighth-largest crypto heist of all time and the largest this year.

BleepingComputer contacted DMM Bitcoin with questions about the breach but a reply was not immediately available.