The World Athletics Championships was rocked by a drugs scandal on Tuesday after coach Alberto Salazar was banned for doping, dealing a fresh body blow to the image of track and field at the sport's showpiece event.
Salazar, best known for coaching Britain's four-time Olympic champion Mo Farah, was handed a four-year ban by the United States Anti-Doping Agency (Usada) for a catalogue of drugs violations.
The 61-year-old Cuban-born American was suspended following a years-long investigation by Usada and a prolonged battle behind closed doors, the agency said.
Jeffrey Brown, a Texas endocrinologist who treated many of Salazar's athletes at his Nike-backed Oregon Project, was also suspended for four years.
Salazar, who has denied the allegations against him, was barred from attending any World Championships venues after having his credentials deactivated, the IAAF confirmed Tuesday.
Salazar is not a member of the United States Track and Field Federation team in Qatar, but several athletes linked to his Nike Oregon Project training group are competing at the championships.
They include the Netherlands' Ethiopian-born runner Sifan Hassan, who romped to victory in the 10,000 metres on Saturday. Hassan is expected to run again later this week.
United States runners Donovan Brazier and Clayton Murphy, both Oregon Project athletes, will compete in Tuesday's 800m final.
None of the athletes taking part at the world championships linked to Salazar have been found guilty of doping offences, and none were implicated in Usada's 134-page summary of the case.
In announcing the bans against Salazar and Brown, Usada praised other athletes for speaking out.
"The athletes in these cases found the courage to speak out and ultimately exposed the truth," said Usada chief executive Travis Tygart.
"While acting in connection with the Nike Oregon Project, Mr Salazar and Dr Brown demonstrated that winning was more important than the health and wellbeing of the athletes they were sworn to protect."
Usada said in the statement that two three-member arbitration panels had determined Salazar and Brown should be banned for "orchestrating and facilitating prohibited doping conduct".
Salazar was discovered to have trafficked or attempted to traffic the banned substance testosterone, given athletes a substance in excess of its permitted limit and tampered with the doping control process of athletes.
"Usada's investigation yielded a wide range of evidence referenced in the hearing, including eye-witness proof, testimonies, contemporaneous emails, and patient records," Usada said.
"Between the two cases, Usada relied on more than 2,000 exhibits, which the AAA heard along with the defendants' cases. In all, the proceedings included 30 witnesses and 5,780 pages of transcripts."
In a statement on the Oregon Project's website, Salazar, a former top marathon runner, denied ever doping his athletes.
"I am shocked by the outcome today," Salazar said. "Throughout this six-year investigation my athletes and I have endured unjust, unethical and highly damaging treatment from Usada.
"I have always ensured the Wada code is strictly followed. The Oregon Project has never and will never permit doping. I will appeal and look forward to this unfair and protracted process reaching the conclusion I know to be true."
Arguably Salazar's greatest achievement was helping to transform British star Farah into a four-time Olympic champion, winning back-to-back 5,000m and 10,000m titles at the 2012 and 2016 Games in London and Rio.
Farah left Salazar's camp in 2017 but denied the decision was related to accusations of doping at the Oregon Project. The Briton has repeatedly denied any knowledge of Salazar's alleged involvement in doping.
"I am a firm believer in clean sport and I strongly believe that anyone who breaks the rules should be punished," Farah said when announcing his split with Salazar. "If I had ever had any reason to doubt Alberto, I would not have stood by him all this time."