Chelsea have confirmed they have been contacted by the Football Association after winger Mykhailo Mudryk returned a negative result in a routine urine test.
The Ukrainian international, who has played 15 games for the Blues this season, denies knowingly taking banned substances.
A statement from Chelsea said: “Chelsea Football Club can confirm that the Football Association recently contacted our player Mykhailo Mudryk regarding a negative result from a routine urine test.
“Both the club and Mykhailo fully support the FA’s testing program and all of our players, including Mykhailo, are tested regularly.
“Mykhailo has categorically confirmed that he has never knowingly consumed banned substances.
“Both Mykhailo and the club will now work with the relevant authorities to find out what led to the negative finding.
“The club will not comment further.”
The Athletic reported, citing multiple sources, that Mudryk tested positive for meldonium after playing for Ukraine in November. Meldonium can aid an athlete’s recovery after strenuous exercise and was added to the World Anti-Doping Agency (WADA) banned list in January 2016.
Mudryk said on social media: “I can confirm that I was informed that a sample I provided to the FA contained a banned substance.”
“This came as a complete shock as I have never knowingly used banned substances or broken any rules and am working closely with my team to investigate how this could have happened.
“I know I didn’t do anything wrong and I hope I can be back on the pitch soon. Due to the confidential nature of the proceedings, I cannot say anything more now, but I will do so as soon as possible.”
Mudryk, who has missed Chelsea’s last five games against the club due to illness, joined the west Londoners from Shakhtar Donetsk last January for a fee that could rise to £88 million. He struggled to secure a regular place in the first team and played predominantly in the second team that took part in cup competitions this season.