WMG spokesman, Will Tanous confirmed to Reuters on Friday that:

"As part of an industry-wide investigation concerning pricing of digital music downloads, we received a subpoena from Attorney General Spitzer's office as disclosed in our public filings. We are cooperating fully with the enquiry."

It was subsequently reported that Sony and Vivendi Universal have also been subpoenaed by the AG's office in connection with the investigation.

Although Mr Spitzer's office has not yet made clear the exact nature of the probe, observers have suggested that it is likely to examine whether Warner, Sony, EMI and Vivendi conspired to fix wholesale pricing for the downloading of music over the internet.