The world’s biggest cryptocurrency exchange is investigating an apparent multibillion-dollar hack, with US$3 billion ($5.3 billion) of crypto assets already frozen and estimates suggesting the amount stolen could be substantially larger.

Binance, the world’s largest cryptocurrency exchange, initially said US$2.54 billion in crypto assets had been frozen as it investigated a potential security breach, with stablecoin issuers Circle and Tether among those freezing related assets.

That figure has now risen to US$3 billion, while crypto-tracking firm Chainalysis estimates US$5.912 billion was stolen at the time of the suspected hack. Binance has not yet confirmed the total amount stolen.

Binance co-founder Yi He said the exchange would “cover…