Liverpool defender Mamadou Sakho was on Thursday provisionally suspended for 30 days after failing a drugs test, European football's governing body UEFA announced.
The France international reportedly tested positive for a fat burner after Liverpool's 1-1 draw against Manchester United in the Europa League on March 17.
"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 17 March," UEFA confirmed in a statement.
It added: "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."
A date for the hearing has yet to be fixed.