Godolphin trainer Mahmood Al Zarooni will stand before a disciplinary panel of the British Horseracing Authority on Thursday afternoon after samples taken from 11 of his horses were found to have contained traces of anabolic steroids.
Al Zarooni could lose his training licence in one of the most significant doping scandals in recent racing history.
The hearing will be held at 2.30pm at BHA headquarters in London.
The 37-year-old has officially been charged with rule breaches related to prohibited substances, duty to keep medication records, and conduct prejudicial to racing.
The BHA said today information provided by Al Zarooni to investigating officers revealed that, in addition to the 11 horses which had initially tested positive, four other horses - Comitas, Sashiko, Vacationer and Tearless - were administered one of two prohibited substances.
Those horses were under the care of the Newmarket trainer, but had not been subjected to testing.
Although Comitas, Sashiko, Vacationer and Tearless were not tested and no positive samples exist, Al Zarooni faces further charges in relation to medication records and conduct prejudicial to racing.
Al Zarooni is one of two British-based trainers responsible for the horses of powerful owners Godolphin, the brainchild of Dubai ruler Sheikh Mohammed.
Samples were taken earlier this month from 45 horses trained by Al Zarooni at Moulton Paddocks Stables, Newmarket.
Subsequent analysis revealed 11 of the samples contained ethylestranol and stanozolol, which are prohibited substances.
Al Zarooni has trained a host of big-race winners, including victory in the 1000 Guineas with Blue Bunting in 2011, since joining the Godolphin team in March 2010.
Last year he won the Ladbrokes St Leger at Doncaster last year with Encke and the richest race in the world, the Dubai World Cup, with Monterosso.
Al Zarooni said on Monday he had made a “catastrophic error” in using the banned substances, saying he did not realise he had broken the rules as the horses were not racing at that time.
Godolphin racing manger Simon Crisford said in a statement on Monday: "His Highness Sheikh Mohammed was absolutely appalled when he was told and this is completely unacceptable to him.
“We will await the outcome of the BHA inquiry before taking any further internal action. Sheikh Mohammed has instructed me to begin an urgent review of all of our procedures and controls. That is already under way and we will take advice from the BHA in completing it.”
