Juventus midfielder Paul Pogba's failed drugs test has been confirmed after his B sample tested positive.
Pogba, 30, was provisionally suspended last month after his initial sample found elevated levels of testosterone in his system.
The France international was selected for random testing after Juve's 3-0 win at Udinese on 20 August, when he had been an unused substitute.
If found guilty of doping, he could be banned for between two and four years.
After Pogba's initial suspension in September, Nato said he had violated anti-doping rules when it found the prohibited substance "non-endogenous testosterone metabolites" and the results were "consistent with the exogenous origin of the target compounds".
Testosterone is a hormone that increases the endurance of athletes.
Speaking at the time of the initial suspension, Pogba's agent, Rafaela Pimenta, said: "What is certain is that Paul Pogba never wanted to break a rule."
Juventus re-signed Pogba on a four-year deal in July 2022 after the player ran down his contract at Manchester United and left as a free agent.
However, Pogba's return to Turin has been beset by persistent injury problems which also saw him miss last year's World Cup in Qatar.
Pogba has played a total of 51 minutes as a substitute this season in games with Bologna and Empoli.
Last season he managed 108 minutes over six Serie A games, three brief appearances and one assist in the Europa League, and 11 minutes in the Coppa Italia - a total of 162 minutes and no goals.
Pogba's injury problems resurfaced recently, with Juventus boss Massimo Allegri saying the player picked up a minor back problem following his appearance against Empoli.
