Tether, the company behind a digital token (USDT) backed by the US dollar, has announced that funds worth over $30 million were “improperly removed” from its wallet by an external attacker.

In an online post, the company said:

“$30,950,010 USDT was removed from the Tether Treasury wallet on November 19, 2017 and sent to an unauthorized bitcoin address. As Tether is the issuer of the USDT managed asset, we will not redeem any of the stolen tokens, and we are in the process of attempting token recovery to prevent them from entering the broader ecosystem. The attacker is holding funds in the following address: 16tg2RJuEPtZooy18Wxn2me2RhUdC94N7r. If you receive any USDT tokens from the above address, or from any downstream address that receives these tokens, do not accept them, as they have been flagged and will not be redeemable by Tether for USD.”

Tether said that following the attack, it has suspended the backend wallet service. In addition, it said that it is providing new builds of Omni Core to the community, which would prevent any movement of the stolen coins from the attacker’s address.

The company further explained that the software is effectively a temporary hard fork to the Omni Layer as it will cause a consensus change to currently running Omni Core clients. It added:

“We are working with the Omni Foundation to investigate ways that will allow Tether to reclaim stranded tokens and rectify the hard fork created by the above software. Once this protocol enhancement is complete, the Omni Foundation will provide updated binaries for all integrators to install. These builds will supersede the binaries provided above by Tether.to. After the protocol upgrades to the Omni Layer are in place, Tether will reclaim the stolen tokens and return them to treasury.”

Underscoring the growing controversy around Tether, CoinDesk brought to the forefront the unclear relationship between Tether and Bitfinex bitcoin exchange. It noted that the two companies share common ownership reportedly, adding that Bitfinex has been accused of using the asset for fraud and market manipulation.