Stablecoin issuer Tether froze three Ethereum addresses on Thursday, holding over $160 million worth of USDT, according to data from Etherscan.
The three accounts will now not be able to move funds.
In total, Tether has blacklisted 563 addresses on the Ethereum blockchain since November 2017, according to the Bloxy block explorer.
Tether has said in the past that it regularly works with regulators to supervise suspicious accounts.
An address with over $1 million in USDT was frozen in late December.
Tether, which issues tokens on several blockchains, began blacklisting addresses following a November 2017 breach in which the firm said $30 million of USDT was stolen.