Liverpool defender Mamadou Sakho has been suspended for 30 days after UEFA opened disciplinary proceedings against him following his doping violation.
The 26-year-old France international is understood to have returned a positive test for a fat-burning substance after the Europa League game at Manchester United on March 17.
The news of the doping violation emerged ahead of Liverpool's home fixture against Newcastle at Anfield on Saturday and he was omitted from the Reds' team as a result, although he was not suspended by the club at the time.
Sakho was also not on the team's flight to Spain on Wednesday lunchtime for Thursday's Europa League clash with Villarreal, as Liverpool and the player had jointly agreed he would remain unavailable for selection.
However, UEFA has now provisionally suspended Sakho for 30 days after he decided not to have his B sample tested ahead of Tuesday's deadline.
A statement from European football's governing body read: "Disciplinary proceedings have been instigated against Liverpool FC player Mamadou Sakho, following the UEFA Europa League round of 16 second-leg match between Manchester United FC and Liverpool FC (1-1), played on March 17.
"The proceedings relate to a violation of the UEFA anti-doping regulations, after the player failed a doping test at the above-mentioned match.
"The player did not request the analysis of the B sample. UEFA has now suspended the player provisionally for 30 days until a final decision is taken by the UEFA control, ethics and disciplinary body.
"The date of the disciplinary hearing will be announced at a later stage."
Sakho's Liverpool team-mate Kolo Toure, who replaced him in the side for the 2-2 draw with Newcastle, was banned for six months in 2011 while at Manchester City after the FA found him guilty of taking slimming tablets.
A similar ban for Sakho - if he is found guilty at the disciplinary hearing - would rule him out of Euro 2016 in France this summer.
France coach Didier Deschamps is set to announce his 23-man squad for Euro 2016 on May 12, more than two weeks before Sakho's provisional ban expires.