Dan Carter and Joe Rokocoko have not broken any doping rules, says the former All Blacks' French club.
In a statement released tonight, Racing 92 said all medical procedures the players went through had followed national and international anti-doping rules.
French newspaper L'Equipe claims "traces of corticosteroids" were found in the urine samples produced by the Racing pair when all players were tested by the French anti-doping agency ahead of June's Top 14 final.
Racing said the treatment both players received was several days before the Top 14 final - but did not require a TUE (therapeutic usage exemption).
"Racing 92 would like to strongly declare that its ethics and its sporting practice are in no way linked with illegal practices," the statement said. "We side with the law, with ethics and we abide by the values of a clean sport."
The statement added that Carter, Rokocoko and Juan Imhoff were "exemplary of what we expect in terms of the behavior, generosity and ethics of our time."
Carter and Rokocoko's management company also backed the pair, saying they had been "aware of the issue for a few weeks".
Simon Porter - a player manager from the Essentially Group, which represent both players - said he has known of the situation for some time, and insisted the pair had TUEs in place, meaning they were allowed to take prescribed medicines.