Frankie Dettori
(Healy Racing Photos)

Christopher Stewart-Moore issued a statement on the rider's behalf yesterday, stating he will face a hearing before the Medical Committee of France Galop next week.

He told BBC Sport today: "There are a large variety of substances which are banned by France Galop.

"We are not going to say which substance he has tested positive for as that would be in breach of their rules, but it's not a performance-enhancing drug."

Dettori had four rides at Longchamp on September 16, the day of the test, an afternoon of major trials for the Prix de l'Arc de Triomphe meeting the following month.

France Galop have not commented on proceedings and in previous similar cases they have not issued a statement before a hearing.

Dettori made the headlines last month when his 18-year association with Godolphin came to an end, with the three-times champion jockey planning to ride as a freelance in 2013.