Top coach Alberto Salazar, banned for four years following a doping probe, used athletes as "laboratory animals", the US Anti-Doping Agency's chief Travis Tygart said Wednesday.
The World Athletics Championships, currently taking place in Doha, was rocked by the scandal on Tuesday and Salazar, 61, was stripped of his accreditation.
The former top marathon runner has denied ever doping his athletes and vowed to appeal.
However Tygart told German broadcaster ZDF that athletes in Salazar's Nike-backed Oregon Project (NOP) training group were kept in the dark about the substances they were given, including whether they were illegal or not.
He pointed out that "no athlete currently at the World Championships in Doha is concerned".
"You must understand that the athletes really had no idea what was going on with them, what was being given to them," Tygart said in a interview broadcast Wednesday.
"What dosage, whether the methods were forbidden or not, they didn't even know."
The investigations that led to Salazar's four-year suspension relate to the years from 2010 to 2014.
Tygart cited examples of athletes being treated like "laboratory animals".
"An athlete was even told she needed medication for a myoma (a tumour of the uterus), even though she didn't have a myoma at all," said Tygart.
"They lied to the athletes and did their medical experiments on them in the NOP."
The anti-doping specialist claims athletes "were simply sent to the doctor and they were told they must listen to and trust him".
Tygart gave an insight into the investigations after 10 athletes from the Oregon Project helped USADA investigators.
"All of them provided us with their medical evaluations," Tygart said.
"We found out they were fake and false information was added after we officially requested it."
The 48-year-old says the environment created within the project "tried to hide everything" and Tygart directly attacked sporting goods giant Nike.
"I hope Nike now sees this as a wake-up call," he said, "They can't find any excuses anymore, they have to admit that experiments were done on athletes in their name and on their premises, and that that was just wrong."
Nike has vowed to back Salazar, saying the USADA sanction "had nothing to do with administering banned substances to any Oregon Project athlete."
Two members of the Oregon Project have won gold medals at the worlds in Doha, including American Donavan Brazier, who powered to victory in Tuesday's 800m final in a championship record time.
However, none of the athletes taking part at the world champions linked to Salazar have been found guilty of doping offences, and none were implicated in USADA's 134-page summary of the case.
Alongside Salazar, Jeffrey Brown, a Texas endocrinologist who treated many of the athletes at the Oregon training hub in Portland, was also suspended for four years.
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