A report from Zorya Londonsk claimed that the £89m man had tested positive for a banned substance in a drugs test that was conducted at the end of October.
Mudryk has not played any football since November 28, being left out of four squads for games that have taken place between December 4 and December 15.
His absence was initially put down to illness by head coach Enzo Maresca, but Chelsea have since confirmed the recent development in an official statement on Tuesday morning.
Moments after the Premier League giants posted their response, Mudryk did the same on social media.
"I know that I have not done anything wrong"
Commenting on his official Instagram account, Mudryk said: "I can confirm that I have been notified that a sample I provided to The FA contained a banned substance.
'This has come as a complete shock as I have never knowingly used any banned substances or broken any rules, and am working closely with my team to investigate how this could have happened.
'I know that I have not done anything wrong and remain hopeful that I will be back on the pitch soon.
"I cannot say any more now due to the confidentiality of the process, but I will as soon as I can (blue heart emoji)."
What happens next?
The initial report claimed that all parties were awaiting for the 'B' sample' to be opened, something which is expected to occur over the coming days.
Mudryk has allegedly been provisionally suspended by the Football Association, but the Daily Mail claims that a law firm representing the player has stated that he has not been charged with a doping offence.
Furthermore, the outlet say that Mudryk is of the opinion that the issue has arisen due to a contaminated supplement. The alleged substance is not available in England.
He is said to have passed another drug test as recently as August.
Written by
Darren Plant