The Italian Olympic Committee's (CONI) anti-doping prosecutor Ettore Torri has opened an investigation and will question Cannavaro on Friday.
Cannavaro, who helped Italy win the World Cup in Berlin three years ago, was already suspended for the country's World Cup qualifier with Ireland on Saturday, but he is expected to join the team for Wednesday's game against Cyprus.
It is not known when Cannavaro tested positive, but CONI said Torri would hold a hearing with the defender and the physician involved in the case.
The player requested an exemption after being treated in hospital but did not receive it before he was dope tested and CONI said that after the exemption request arrived it had written to the player asking for a doctor's certificate.
"After an Italian player made a request for an exemption for therapeutic reasons for medicine given in an emergency, CONI's Therapeutic Exemption Committee requested via registered letter that the Emergency Room doctor's certificate be added to the documentation sent," CONI said on its website. "In the meantime, the athlete was subjected to an anti-doping test and the result was positive."
Juventus have said that they will co-operate with the investigation, claiming on their website: ''With regards to the news of the launch of an investigation by the Procura Antidoping involving player Fabio Cannavaro, the medical division of Juventus state that they acted within the sanitary prescriptions and the deontological rules, intervening in an urgent manner - last August - following the worsening of the clinical condition following the sting by an insect.
''On that occasion a medical remedy which was indispensable in order to prevent eventual complications, even lethal ones, was used. The player and the medical staff of Juventus will be at the disposal of the Procura to clarify this issue as soon as possible, as well as eventual documentation.''
It is not the first time Cannavaro has been in trouble. In 2005, a video was shown on Italian TV of the defender being injected with a performance-enhancing substance the night before the 1999 UEFA Cup final. The sequence was shot in a Moscow hotel room, shortly before his Parma team beat Marseille 3-0 for the title.
The substance was Neoton, a creatine phosphate, that was not on any banned lists in Italy at the time.
