British sprinter Chijindu Ujah has been suspended from competition after testing positive for a banned substance.
With the Tokyo 2020 Olympic Games over less than a week doubt has already begun to emerge over medals.
Ujah, 27, was part of Team GB men's 4x100m relay team which won silver, coming home behind Italy and ahead of Canada.
The Athletics Integrity Unit (AIT) says they have started disciplinary proceedings against four athletes asserted to have breached anti-doping rules at the Games.
Ujah, who was part of the team which clocked a time of 37.51, is one of them.
The AIU has started disciplinary proceedings against 4 athletes asserted to have breached anti-doping rules @Tokyo2020 , following testing by @IntTestAgency.
Sadik Mikhou 🇧🇭
Benik Abramyan 🇬🇪
Mark Otieno Odhiambo 🇰🇪
Chijindu Ujah 🇬🇧
— Athletics Integrity Unit (@aiu_athletics) August 12, 2021
A statement from the International Testing Agency (ITA) on Thursday evening said;
"A sample collected from Ujah Chijindu, sprinter from Great Britain, has returned an adverse analytical finding (AAF) for Sars Enobosarm (Ostarine) and Sarms S-23 (S1.2 "Other anabolic agents" - "selective androgen receptor modulators").
"The sample was collected by the ITA under the Testing Authority of the International Olympic Committee (IOC) during an in-competition anti-doping control on 6 August 2021 in Tokyo, Japan, following the final of the Men’s 4 x 100m Relay Final of the Olympic Games Tokyo 2020.
"The result was reported by the WADA-accredited laboratory of Tokyo on 8 August 2021.
"The athlete has the right to request the analysis of the B-sample.
"If requested by the athlete and if the B-sample analysis confirms the AAF, or alternatively if the athlete does not wish to have the B-sample analysis undertaken, the case will be referred to the Anti-Doping Division of the Court of Arbitration for Sport (CAS ADD) for adjudication under the IOC Anti-Doping Rules applicable to the Olympic Games Tokyo 2020 (IOC ADR)."