About $20 million in cryptocurrency seized from the notorious Bitfinex hack has mysteriously moved out of U.S. government-controlled wallets, blockchain analytics firm Arkham Intelligence reported. The unauthorized transfers started Thursday afternoon and mark what appears to be a major security breach of government-held digital assets.

Suspicious activity was first detected when dormant funds were withdrawn from decentralized lending platform Aave. Assets transferred include approximately $14 million in AUSDC stablecoin, $5.4 million in USDC, $1.1 million in USDT, and nearly half a million dollars worth of ETH.

Blockchain investigators' analysis shows the funds originated from nine different government seizure addresses, one of which was specifically named in court documents related to the Bitfinex case. The suspect then immediately began to launder the funds through several different non-custodial services, in an apparent attempt to obscure the trail of the stolen money.

"We believe the attacker has already begun laundering the proceeds through suspicious addresses linked to a money laundering service," Arkham Intelligence reported. The suspect’s main wallet still holds close to $13 million in crypto assets, but significant parts have already been transferred to second wallets. The two receiving wallets, identified by their addresses starting with 0x15D0a and 0xBf6F7, hold approximately $5.5 million and $1.4 million in ETH, respectively.

The 2016 Bitfinex hack initially accounted for only $65 million but gained notoriety after it was reported that the value inflated to over $4 billion, making the recovered funds the single largest seizure in cryptocurrency history under the U.S. government. The funds recovered stemmed from the high-profile arrest of Heather "Razzlekham" Morgan and Ilya Lichtenstein.