U.S. cryptocurrency expert Virgil Griffith ignored explicit warnings from the FBI to cease dealings with North Korea ahead of his arrest for helping the country evade sanctions, the law enforcement agency told NK News in an exclusive interview.

Prosecutors accused Griffith of participating in an April 2019 Pyongyang conference to talk about “potential money laundering and sanction evasion applications” of crypto and blocktain technologies, and the FBI said he continued North Korea-related activities after the conference despite clear warnings.