One of the world's best known athletics coaches is at the centre of doping allegations, according to a BBC investigation.
Alberto Salazar has been accused of violating anti-doping rules, including claims he was involved in doping US record holder Galen Rupp, in 2002.
Rupp and GB Olympic gold medallist Mo Farah are part of Salazar's US stable, the Nike Oregon Project. There is no suggestion Farah has broken any rules.
Salazar and Rupp deny any wrongdoing.
Salazar is a US athletics legend, who won the New York marathon three years in a row and ran himself unconscious in winning the Boston marathon in 1982.
He is now one of the world's most successful coaches. The head coach at the prestigious Nike running camp based in Portland, Oregon, Salazar has worked with Farah since 2011 and has coached his training partner Rupp for 14 years.
His coaching philosophy involves intensive training and the use of the latest scientific techniques.
Rupp is the US 10,000m record holder and was 10,000m silver medallist at the London Olympics, behind Farah.
None of the Nike Oregon Project (NOP) athletes has ever failed a drug test. But the BBC has heard claims about some of Salazar's methods including the use of banned steroids and unethical practices.
Galen Rupp is the US 10,000m record holder and was 10,000m silver medallist at the London Olympics
The BBC is aware of at least seven athletes or staff associated with the NOP who say they have gone to the US Anti-Doping Agency (Usada) with their concerns, though Usada does not confirm or deny investigations.
The allegations, which come from a number of former athletes and staff, will feature in a BBC documentary on Wednesday.
The investigation into the Oregon Project - which is a BBC collaboration with US journalism organisation ProPublica - heard claims that American distance runner Rupp had been given the banned anabolic steroid testosterone in 2002, when he was 16 years old.
Steve Magness, who was Salazar's number two at the Oregon Project in 2011, said he saw a document showing Rupp's blood levels, which said the athlete was on "testosterone medication".
"When I saw that, I kind of jumped backwards," Magness said.
"Testosterone is obviously banned... everybody knew that.
Steve Magness became a coach after his athletics career ended prematurely because of injury
"When I looked a little further I saw it was all the way back in high school - and that was incredibly shocking."
Since 2003, Wada (World Anti-Doping Agency) rules have stipulated that athlete support personnel involved in doping someone as young as 16 could be liable for a lifetime ban.
Magness claimed when he questioned the coach about the document, Salazar said it had been a mistake.
The 30-year-old left Nike after the 2012 London Olympics and went to Usada with his story.
Salazar declined to be interviewed for the programme. But in a statement he told the BBC the legal nutritional supplement Testoboost had been incorrectly recorded in the document as "testosterone medication".
He added the "allegations your sources are making are based upon false assumptions and half-truths in an attempt to further their personal agendas".
Rupp, who is one of America's most drug tested athletes, strenuously denied ever using testosterone or testosterone medication.
The 29-year-old added: "I am completely against the use of performance enhancing drugs.
Salazar is one of the world's most successful coaches
"I have not taken any banned substances and Alberto has never suggested that I take a banned substance."
