MILAN, April 11 (Reuters) - Italy's communications authority (AGCOM) is set to decide on April 18 whether stake building by France's Vivendi in Italian broadcaster Mediaset breaches Italian antitrust regulations, a source close to the matter said on Tuesday.
AGCOM opened an investigation into the French media company on Dec. 21, after Mediaset filed a complaint regarding Vivendi rapidly accumulating a 28.8 percent share.
The source said the board of AGCOM started a discussion on its findings in the Mediaset-Vivendi case on Tuesday and was likely to reach a conclusion by April 18.
The authority has to decide whether Vivendi, which also holds a 24 percent share in phone incumbent Telecom Italia , breaches a national law which prevents companies from having an excessive share in both the domestic telecommunications and media markets.
Vivendi declined to comment. (Reporting by Francesca Piscioneri,; Additional reporting by Gwenaelle Barzic in Paris,; Writing by Giulia Segreti,; Editing by Giselda Vagnoni)