More than 50,000 digital files, including some of Michael Jackson's back catalogue, has been stolen from Sony's website by hackers. Sony acquired the rights to Jackson's material in a multi-million dollar deal and subsequently released the King of Pop's first posthumous album Michael in December of 2010.

Jackson's unreleased material includes high-profile duets with Freddie Mercury and will.iam but it's not immediately obvious whether or not they were among the leaked tracks.

The online theft is understood to have taken place shortly after Sony's Playstation network was compromised in April last year.