The Italy international and Fiorentina captain was found dead in his hotel room in the north-eastern city of Udine on March 4 ahead of a Serie A match against Udinese.
Football stands in Ferguson support
An initial post mortem suggested the 31-year-old died due to bradyarrhythmia when the heart slows so much it stops -- but the causes of this are unclear.
According to the Corriere Fiorentino newspaper and Italian news agencies, doctors Carlo Moreschi and Gaetano Thiene have asked the public prosecutor for another 30 days for further investigations including more toxicology tests, as well as genetic testing.
An investigation was opened into possible manslaughter, which is standard procedure in Italy when a death is unexplained.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ