All Black legends Dan Carter and Joe Rokocoko, alongside Racing 92 team-mate Juan Imhoff, were interviewed by French Rugby anti-doping chiefs on Wednesday after testing positive for corticosteroids.
The three gave back positive readings after being drug-tested following June's Top 14 final against Toulon in Barcelona, won by Racing 29-21.
Each player was accompanied by a lawyer as they turned up at the French Rugby Federation (FFR) headquarters at Marcoussis, near Paris, on Wednesday morning.
Their positive tests were revealed by French sports newspaper L'Equipe last week.
Corticosteroids can be used to combat pain, inflammation or allergies.
They can be taken legally or illegally, depending on the method of ingestion.
It is illegal to take corticosteroids orally or have them injected in either the blood or muscle, but they can be injected into joints or inhaled.
Even if taken in a banned manner, athletes can gain permission to do so by applying for the controversial Therapeutic Use Exemption (TUE).
A five-man panel of the FFR anti-doping commission will decide whether or not the players, and Racing, have broken any rules.
Racing informed French anti-doping (AFLD) officers that the players had taken corticosteroids at the time of their drug tests.
Now the panel must decide whether or not the results correspond with Racing's version of the time, quantity and method of administration.
Racing claimed the players were administered a treatment "by authorised method" due to "known conditions" from which they were suffering, "several days before the Top 14 final" and which "didn't need a TUE".
French television channel Canal+ claimed Carter's corticosteroid readings showed 81 nanogrammes par millilitre, with 49 for Rokocoko and 31 for Imhoff, while the World Anti-Doping Agency (WADA) has set a limit of 30.