Essendon AFL players were used as virtual human guinea pigs by the club, according to Fairfax Media, receiving a banned substance at a volume and frequency far exceeding that of its clinical trials.
Fairfax says the Australian Sports Anti-Doping Authority is investigating whether the performance of players given certain supplements, including AOD-9604, was measured against teammates who had not received the drugs and whether results were passed to external parties.
AOD-9604 is not approved for human use but a yet-to-be-determined number of players are understood to have been regularly jabbed with the substance over several months last year.
According to Fairfax, the clinical trial showed the substance was ineffective as a fat-buster and trial participants reported 118 adverse events, three deemed severe.
Essendon captain Jobe Watson admitted last week that he was injected with AOD-9604, which is banned by the World Anti-Doping Agency (Wada) because it is not approved for human use.
Fairfax quoted a source familiar with the inquiry who said: "Wada were shocked by some of the substances going around Essendon and some of the NRL clubs.
"Some of those drugs had not been thought of in a sporting context before. We've got a playing generation of guinea pigs."
The AFL said it would not comment on "claims and speculation related to the case".