The mystery over the cyber attack on Sony Pictures deepened Tuesday as some U.S. investigators now suspect North Korea hired outside hackers to try to stop the release of a comedy about the assassination of dictator Kim Jong-un.

North Korea needed to hire hackers because the backwards, Stalinist nation lacks the technical skills to launch what has been called the most destructive and sophisticated computer attack against a major corporation in the United States, one investigator told London’s Guardian newspaper.

The hackers stole massive amounts of personal information on Sony employees, wiped computer hard drives clean of data and crashed most of the studio’s network for more than a week last month.

The FBI, conducting its own investigation into the cyber attack, says North Korea acted alone.

“The FBI has concluded the government of North Korea is responsible for the theft and destruction of data on the network of Sony Pictures Entertainment,” the bureau told the Guardian.

In another development, two shadowy hacker groups have now claimed a role in the cyber attack.

The so-called Guardians of Peace first boasted that it brought down the Sony network to protest the scheduled Christmas Day release of the film “The Interview.” Another group, called the Lizard Squad, says it supplied the Guardians with several Sony employee logins, which helped the hackers breach the network’s security wall.

A hacker who claimed to be with the Lizard Squad told The Washington Post that the group “handed over some Sony employee logins” to the Guardians “for the initial hack.”

The Lizard Squad has also claimed credit for disrupting the PlayStation and Xbox online gaming networks on Christmas Day.

Sony Pictures initially relented to the cyber attack and agreed to postpone the release of the film. But, after widespread criticism, the studio sent the movie to 331 independent cinemas and brought in $1 million on opening day. Sony also released the film online and has earned nearly $18 million through both movie theaters and the Internet.

The film, starring Seth Rogen and James Franco, cost $44 million to make and was expected to earn $20 million over its first weekend.

Related Stories:

• Sony's 'The Interview' Packs Theaters Without Promised Violence
  
• PlayStation Cyberattack Downs Network During Prime Gaming Days