Music
The song, titled 'Don't Let Me Down', is sung by Lewis and labelled as being produced by Justin Timberlake and Timbaland, The Sun reports.
A spokesman for Sony BMG subsidiary Syco said: "Syco are working alongside the International Federation of the Phonographic Industry, the British Phonographic Industry, the police and investigators in this and they are making fast progress.
"We will certainly look to bring charges against those who are responsible. We cannot give any more details at this stage for operational reasons."
Last month, it was claimed that staff at the label were "furious" at the leak of demo tracks by fellow X Factor winner Alexandra Burke.
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