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A senior FBI official, speaking at a cyber security conference, said the agency hasn’t confirmed North Korea’s involvement in the hacking attack on Sony Pictures Entertainment, according to Reuters.

“There is no attribution to North Korea at this point,” Joe Demarest, assistant director with the FBI’s cyber division, said in remarks made while speaking on a cyber security panel in Washington, D.C. He added the agency hasn’t confirmed any government’s involvement.

A previously unknown group calling itself the Guardians of Peace has claimed responsibility for the breach, which resulted in the public release of salary information, private emails and confidential contracts. Re/code first reported on Nov. 28 that an internal investigation was examining a possible North Korean link to the attack.

The group called on Sony to halt distribution of what it called “the movie of terrorism” — an apparent reference to “The Interview,” a comedy starring Seth Rogen and James Franco as TV journalists chosen to conduct a rare interview with North Korea leader Kim Jong-Un. The two are then recruited by the CIA to try and assassinate Kim.

The North Korean government has denied involvement, but praised the attackers.

Neither the FBI nor Sony responded to requests seeking comment.