Paul Pogba's backup B sample has also tested positive for testosterone, meaning the Juventus midfielder now faces a doping investigation.
The exams were carried out by Nado Italia, Italy's anti-doping agency, which suspended Pogba provisionally nearly a month ago following a positive test carried out after Juventus' game at Udinese on Aug. 20. Pogba did not play in the Serie A match but was on Juve's bench.
Pogba remains suspended provisionally and risks a ban of up to four years.
Neither Pogba nor Juventus has publicly contested the results of the tests.
"Humanely, I'm sorry for Paul," Juventus coach Massimiliano Allegri said Friday.
The doping case is another negative note for a player who has been bothered by injuries ever since rejoining Juventus from Manchester United a little more than a year ago.
He was ruled out of France's run to the World Cup final last year because of a knee injury and played in only six Serie A matches for Juventus last season.
There's also been a police investigation ongoing in France into allegations Pogba was targeted by extortionists -- including by his older brother Mathias, who has denied any wrongdoing.