London (AFP) - Liverpool defender Mamadou Sakho is being investigated by UEFA over a possible anti-doping rule violation, the Premier League club revealed on Saturday.
Sakho has not been suspended over the potential violation, but Liverpool have decided to leave out the France international while the probe continues and he was absent from the squad for Saturday's league fixture against Newcastle United at Anfield.
UEFA said that Sakho gave an "adverse finding" in a test after the Reds' match against Manchester United in the Europa League on March 17.
Reports in France claim Sakho tested positive for a fat burner after the 1-1 draw.
"Yesterday, Friday 22nd April 2016, a formal communication was received from UEFA stating that they are investigating a possible anti-doping rule violation by Mamadou Sakho," a statement on Liverpool's website read.
"The player will respond to UEFA on the matter. The player is currently not subject to any playing suspension.
"However, the club, in consultation with the player, has decided that while this process is followed the player will not be available for selection for matches."
UEFA later confirmed the news and said that Sakho, who has 28 caps for France, has until Tuesday to request his B sample be tested.
"UEFA would like to confirm the information communicated by Liverpool FC regarding an adverse finding in a doping test of their player Mamadou Sakho conducted at the UEFA Europa League match between Manchester United FC and Liverpool FC on 17 March 2016 (1-1)," European football's governing body said in a statement sent to AFP.
"The player and the club have received all the pertinent information and have until Tuesday to request the analysis of the B sample as well as to provide explanations for the presence of a prohibited substance in the player's body.
"There are no disciplinary proceedings opened at this stage."
The 26-year-old centre-back is said not to have known the composition of the weight-loss supplement and has informed the club he acted in good faith.
Sakho's Liverpool team-mate Kolo Toure was suspended for six months after failing a drugs test while playing for Manchester City in February 2011.
The Ivory Coast defender had tested positive for bendroflumethiazide, a weight-loss drug contained within "water tablets" and apparently recommended by his wife.
If Sakho is unable to prove his innocence it would be a significant blow to Liverpool manager Jurgen Klopp as the former Paris Saint-Germain player has formed a solid partnership alongside Dejan Lovren in recent weeks.
Sakho, who moved to Anfield for Â£18 million ($25 million) in 2013, is in danger of missing the finale to Liverpool's Europa League challenge, with the team facing Villarreal in the semi-final first leg in Spain on Thursday.
He could also miss the Euro 2016 finals in France if he were found guilty and given a long ban.
Sakho started France's last match, a 4-2 friendly win against Russia at the end of March.
Liverpool have made a swift response to the alleged doping violation and consulted fully with UEFA and the English Football Association.
While Sakho is technically still available to play, it was felt by Klopp and Liverpool's US-based owners that the best course of action was to withdraw the player from selection and it is understood Sakho agreed with the decision.
Liverpool won't face disciplinary action as that can only happen if two players in the same season are found to have had doping violations.