Team GB 4x100m relay silver medallist CJ Ujah has been suspended for a suspected doping violation.
The International Testing Agency (ITA) says the relevant sample was collected after the 27-year-old competed in the 4x100m final at the Tokyo Olympics on 6 August.
The result was reported at a laboratory two days later.
He now has the right to request the analysis of his B-sample.
Ujah competed with Richard Kilty, Zharnel Hughes, and Nethaneel Mitchell-Blake. They came runners-up to Italy.