LONDON, Dec 19 (Reuters) - WPP, the world's largest advertising agency, said on Monday that three of its subsidiaries had received subpoenas from the U.S. Department of Justice as part of an investigation into video production practices in the advertising industry.
Run by the high-profile British businessman Martin Sorrell, WPP said that both the group and its subsidiaries were fully cooperating with the enquiries.
The DoJ's antitrust division has been investigating whether advertising agencies rigged bids to favour their in-house production units in competition with independent companies.
Rival groups Interpublic Group of Cos, Omnicom Group and Publicis Group SA had already announced that they had been subpoenaed as part of the investigation.
Shares in WPP were down 0.4 percent at 1,774 pence by 1608 GMT, when the Stoxx 600 Europe Media sector index was up 0.16 percent.
Large advertising companies have expanded their own production operations in recent years as a way to grow new revenue streams and keep up with advertisers' increasing demand for video content.
WPP declined to comment further. (Reporting by Kate Holton; Editing by Greg Mahlich)