Athletics coach Alberto Salazar, whose stable of athletes includes Great Britain's Mo Farah, has been named at the centre of a fresh doping allegation in a television documentary.
Salazar is said to have violated anti-doping rules amid claims another member of his stable in 2012 Olympic silver medallist Galen Rupp, Farah's long-time running partner, has taken the banned anabolic steroid testosterone.
The BBC documentary alleges Rupp started taking the banned substance at the age of 16 under the supervision of Salazar.
Both Salazar and Rupp and have denied any wrongdoing, while there is no suggestion Farah has broken any rules.
The investigation by Panorama follows a number of accusations from inside the Nike Oregon project, the famed training academy in America where Farah has trained since 2011.
Steve Magness, a former aide to Salazar, levelled the most serious allegation in the documentary, which is to be aired at 9pm on Wednesday 3 June.
Magness recalled being in Salazar's office and finding reports indicating Galen's blood levels tested off the charts.
"Under one of Galen's it had 'currently on testosterone and prednisone medication' and when I saw that I kind of jumped backwards," explained Magness. "Testosterone is obviously banned and everyone knew that. It was all the way back in high school – and that was incredibly shocking. At that point I actually took a picture of it. I wanted to essentially to have evidence in case something happened."
In denying such claims, Salazar stressed in a statement issued to the BBC that legal supplement Testoboost had been "incorrectly recorded as 'testosterone' medication", adding "the allegations were based upon false assumptions and half-truths".
Rupp said in his statement: "I have not taken any banned substances and Alberto has never suggested that I take a banned substance."