Team GB sprinter CJ Ujah has said he is "shocked and devastated" by his provisional suspension from competition for an anti‑doping rule violation he received after testing positive for two banned substances.
But on Thursday he was informed of an "adverse analytical finding" from testing that took place during the Games.
The Athletics Integrity Unit said a test showed the "presence/use of a prohibited substance (Ostarine and S-23)," which are known to mimic the properties of testosterone and help with building muscle.
In a statement to the PA news agency, Ujah said it had taken him a few days to process the news.
“I am completely shocked and devastated by this news. To be absolutely clear, I am not a cheat and I have never and would never knowingly take a banned substance," he said.
“I love my sport and I know my responsibilities both as an athlete and as a team-mate. I am respecting the formal processes and will not be making any further comment until it is appropriate to do so.”
If the case against the Team GB sprinter is proven, the British relay quartet, also including Zharnel Hughes, Richard Kilty and Nethaneel Mitchell-Blake, are likely to be stripped of their silver medals.
The AIU confirmed that Bahrain’s 1500m runner Sadik Mikhou, Georgian shot-putter Benik Abramyan and Kenya sprinter Mark Otieno Odhiambo have also been provisionally suspended following adverse tests.