North Korean state-backed hacking collective Lazarus Group is linked to a massive cryptocurrency hack that led to the theft of $615 million in digital assets, U.S. officials allege.

The Treasury Department’s Office of Foreign Assets Control on Thursday announced new sanctions against an ethereum wallet belonging to Lazarus.

According to crypto researchers, the identified wallet contains funds related to an attack on the Ronin Network, which supports the popular blockchain game Axie Infinity. More than $600 million worth of ether and USDC tokens were stolen in the attack.