Dutch investigators said on Friday they arrested an alleged developer of Tornado Cash, a cryptocurrency service sanctioned by Washington for allegedly laundering funds stolen by North Korean hackers.

The 29-year-old was arrested in Amsterdam on Wednesday and will appear before an investigating judge later on Friday, the Dutch Financial and Tax Crime Investigation Service (FIOD) said.

“We suspect a developer … from Tornado Cash of being involved in the concealment and laundering of large-scale criminal money flows by mixing cryptocurrencies,” FIOD said on Twitter.

“Multiple arrests are not excluded.”

The Dutch agency said it has been investigating Tornado Cash since June 2022 on suspicion of laundering at least $1 billion in criminally obtained cryptocurrency, out of a total turnover of $7 billion, she said.

“These included funds stolen through hacks by a group suspected of being associated with North Korea,” he said.

The people behind the service had made “large-scale profits” from these transactions, he said.

Tornado Cash is one of the leading mixers, also known as tumblers, that help people hide the movements of their cryptocurrencies like bitcoin and ethereum by mixing them with other users’ transfers.

The US Treasury imposed sanctions on the Tornado money on Monday.

He said Tornado Cash was used to transfer and hide $455 million of the more than $600 million of Ethereum virtual currency stolen in April from the Axie Infinity game through the Ronin network.

The theft, which the Treasury called the largest known crypto heist to date, was carried out by North Korean state-backed hacking units known as the Lazarus Group and APT38, according to the FBI.

Tornado Cash had also been used to transfer at least $96 million of funds stolen in June from crypto exchange service Harmony Bridge, and another $7.8 million of the nearly $200 million in cryptocurrency hacked. from Nomad, a similar service, the Treasury said.

Roman Semenov, the Russian founder of Tornado Cash, suggested in a statement on Twitter on Monday that his company could not filter who uses the service.