Mo Farah's coach Alberto Salazar has again found himself at the centre of doping allegations after a leaked report alleged he may have abused prescription medicines and drug infusions.
The Sunday Times published a leaked report from the United States Anti-Doping Agency (USADA) which stated that Salazar, the head coach at the Nike Oregon Project in Portland, gave six leading American runners intravenous drip infusions which "almost certainly" broke anti-doping rules.
Salazar has always denied any wrongdoing in relation to his work with athletes at the Oregon training centre, which first surfaced in a BBC Panorama programme in June 2015. Farah has also denied ever having breached anti-doping regulations.
The leaked USADA report says athletes were given infusions of the chemical L-carnitine, a naturally-produced amino acid prescribed as a supplement for heart and muscle disorders. It is not a banned substance for athletes, but infusions of more than 50 millilitres in the space of six hours are prohibited.
The Sunday Times says USADA was also, separately, still investigating the use of L-carnitine by Farah at the time the leaked report was written in March 2016.
The newspaper claims Salazar even boasted to Lance Armstrong of the "amazing" benefits of the drug before the disgraced former cyclist's downfall.
The Sunday Times says that the USADA report contains allegations that Salazar gave athletes, including Farah, prescription drugs they had no medical need for in order to aid performance. For Farah, the Sunday Times says, this included potentially dangerous doses of permitted vitamin D medication to boost his testosterone levels.
The USADA document said that Farah's British doctors intervened over concerns for his health, the Sunday Times reports.
It also reportedly says Farah was given an infusion of L-carnitine shortly before his London marathon debut in 2014 from medical staff at UK Athletics, who were advised by Salazar and his staff. The volume of that infusion is unknown.
UK Athletics, speaking on behalf of the doctor who administered the infusion, said in a statement to the Sunday Times: "To our knowledge, all doses administered and methods of administration have been fully in accordance with WADA (World Anti-doping Agency) approved protocol and guidelines."
The Sunday Times says Farah told them two years ago that he had "tried a legal energy drink" containing L-carnitine, but "saw no benefit" and did not continue with it.
The USADA report also accuses Salazar of looking to impede its investigation, the newspaper claims.
Salazar said athletes were given L-carnitine in "exactly the way USADA directed", the Sunday Times says.
USADA released a statement on Saturday confirming it had prepared a report "in response to a subpoena from a state medical licensing body regarding care given by a physician to athletes associated with the Nike Oregon Project", and that "a draft of this report was leaked to the Sunday Times by the Russian state-affiliated hacker group known as Fancy Bears".
The statement added: "We understand that the licensing body is still deciding its case and as we continue to investigate whether anti-doping rules were broken, no further comment will be made at this time.
"Importantly, all athletes, coaches and others under the jurisdiction of the World Anti-Doping Code are innocent and presumed to have complied with the rules unless and until the established anti-doping process declares otherwise. It is grossly unfair and reckless to state, infer or imply otherwise."
USADA launched an investigation into Salazar following the Panorama programme in the summer of 2015 and Farah was questioned by its lawyers as part of that investigation. But it has never announced it has uncovered any evidence of wrongdoing.
Farah said at the time that his name had been "dragged through the mud", but he has remained loyal to Salazar.
The Briton has won four Olympic and five world titles over 5,000 metres and 10,000m since relocating to the United States to link up with Salazar in 2011. This will be his final season on the track.
Press Association Sport has made efforts to contact Farah's representatives, as well as Nike and UKA, but has yet to receive a response.