London - 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.
Reports in France claim Sakho tested positive for a fat burner after the Reds' 1-1 draw against Manchester United in the Europa League on March 17, but Liverpool have not confirmed those suggestions.
"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."
Sakho, who has 28 caps for France, is said to be ready to request his B sample be tested, with the deadline for that request set for Tuesday.
The 26-year-old centre-back is believed not to have known the composition of the weight-loss supplement and has informed the club he acted in good faith.
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 £18 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.