Carter, fellow All Black Joe Rokocoko and Argentinian Juan Imhoff were all reported by French sports newspaper L'Equipe as having submitted tests showing traces of corticosteroids prednisolone following the final of the French Top 14 rugby competition on June 24.

Each attended a French Rugby Federation (FFR) anti-doping hearing in Marcoussis in October and was subsequently cleared of any wrongdoing.

But, according to Le Monde, the AFLD has requested that all three players now explain how the products got into their bodies.

It is thought that the anti-doping body wishes to determine if the rates of corticosteroids registered are consistent with the treatments reported by the club doctor and with the method by which they were supposedly administered. 

The French newspaper reports that this procedure is "neither rare nor automatic".

Racing 92 have so far refused to comment on the latest reports.

A date has not yet been set for the hearing.

Racing 92 have previously denied that the players breached anti-doping rules or obtained a therepeutic use exemption (TUE) to take otherwise banned substances.

They claim the case relates to "treatment by an authorised channel" and that they are "on the side of law, ethics and love of a clean sport".

Use of some corticosteroids is allowed if injected into a joint, used on the skin or taken nasally.

But a TUE is required if taken orally, injected into a muscle or taken by suppositories.

Carter and Rokocoko's manager Simon Porter suggested that Carter had used a corticoid for treatment of a calf injury, while Rokocoko was recovering from a knee injury.

Imhoff is thought to have used the substance via a nasal spray.

Racing 92 beat rivals Toulon 29-21 in the Top 14 Final at the Nou Camp in Barcelona as World Rugby Player of the Year Carter produced a man of the match performance.