Dubai: Godolphin have initiated an urgent review into procedures and controls related to the operations of one of their racing stables in England after irregularities were found in blood samples taken from several of their horses.

Following an inspection of trainer Mahmoud Al Zarouni’s stable at Moulton Paddocks, Newmarket, by officials from the British Horseracing Authority (BHA), traces of prohibited substances were discovered in 11 of 45 horses tested.

Among the horses that tested positive for anabolic steroids was Certify, one of the favourites for the English 1,000 Guineas, which is scheduled to take place on May 5. The BHA has advised that, as a result, the filly will not be allowed to participate in the race, which the trainer won in 2011 with Blue Bunting.

Al Zarouni was appointed to the Godolphin stable — owned by His Highness Shaikh Mohammad Bin Rashid Al Maktoum, Vice President and Prime Minister of the UAE and Ruler of Dubai — in March 2010.

In a statement on Godolphin’s website, Racing Manager Simon Crisford said: “This is a dark day for Godolphin. We are all shocked by what has happened.

“His Highness Shaikh Mohammad 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.

“Shaikh Mohammad has instructed me to begin an urgent review of all of our procedures and controls. That is already underway and we will take advice from the BHA in completing it.”

Al Zarouni, 37, admitted the wrongdoings, saying: “I deeply regret what has happened. I have made a catastrophic error. Because the horses involved were not racing at the time, I did not realise that what I was doing was in breach of the rules of racing. I can only apologise for the damage this will cause to Godolphin and to racing generally.”

The trainer has been instructed to attend a BHA disciplinary inquiry that will be held as soon as possible.

Godolphin said they would not be making any further comment until the completion of the BHA investigation and inquiry.