Usada investigating coach Alberto Salazar as he denies doping claims
Under-fire trainer issues lengthy statement detailing his rebuttal of story
American coach Alberto Salazar is being investigated by the US Anti-Doping Agency (Usada) to determine if anti-doping rules may have been violated, a source said.
The agency is seeking documents and interviewing witnesses, the person, who is familiar with the investigation, said.
The probe has been ongoing and began before the BBC television programme Panorama in association with American website ProPublica made a series of allegations, the source said.
The allegations included that Salazar had given Olympic 10,000 metres silver medallist Galen Rupp the banned anabolic steroid testosterone.
Rupp is the training partner of British double Olympic champion Mo Farah, who has not been accused of any wrongdoing.