Roughly $625 million worth of cryptocurrency has been stolen from Ronin, the blockchain underlying popular crypto game Axie Infinity.

Ronin and Axie Infinity operator Sky Mavis revealed the breach on Tuesday and froze transactions on the Ronin bridge, which allows depositing and withdrawing funds from the company’s blockchain.

Sky Mavis says it’s working with law enforcement to recover 173,600 Ethereum (currently worth around $600 million) and 25.5 million USDC (a cryptocurrency pegged to the US dollar) from the culprit, who withdrew it from the network on March 23rd.