Britain has been stripped of its Olympic silver medal in the men's 4x100m relay in Tokyo last August after the Court of Arbitration for Sport (CAS) upheld Chijindu Ujah's anti-doping violation on Friday.

Ujah has been provisionally suspended since Ostarine and S-23 -- both substances prohibited by world anti-doping organisation WADA -- were detected in his sample in Tokyo.

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In a statement on Friday, CAS said it had found that Ujah has committed an Anti-Doping Rule Violation and that his result from the 4x100m relay on Aug. 6 had been disqualified.

Ujah and his relay team mates Zharnel Hughes, Richard Kilty and Nethaneel Mitchell-Blake finished second behind Italy.

Canada will now be upgraded to silver with China moving into the bronze medal position.

"I accept the decision issued by the Court of Arbitration for Sport today with sadness," Ujah said in a statement issued by UK Athletics.

"I would like to make it clear that I unknowingly consumed a contaminated supplement and this was the reason why an anti-doping rule violation occurred at the Tokyo Olympic Games.

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"I would like to apologise to my team mates, their families and support teams for the impact which this has had on them. I'm sorry that this situation has cost my teammates the medals they worked so hard and so long for, and which they richly deserved. That is something I will regret for the rest of my life."

UK Athletics added: "UKA continue to be in regular communication with the athletes concerned but will not be making public comment on the case until after the World Athletics/AIU process which will follow on from this CAS outcome."