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."
"They lied to the athletes and did their medical experiments on them in the NOP."
"We found out they were fake and false information was added after we officially requested it."
"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."