(CNN) -- The American-bred horse who won last year's St Leger -- Encke -- is among seven more horses trained by disgraced Godolphin trainer Mahmood Al Zarooni to test positive for steroids, the British Horseracing Authority (BHA) has announced.
Encke won the St Leger last September 2012 as a 25/1 outsider and tested negative for doping after the race.
His surprise victory denied Camelot the chance to become the first Triple Crown winner since 1970, with the winner of the 2,000 Guineas and Epsom Derby finishing in second place.
The feat of winning the three races is so rare that only one horse has achieved it since the second world war - Nijinsky in 1970.
After Al Zarooni earned an eight-year suspension when he admitted administering banned drugs to 15 horses in his care, the BHA undertook further extensive testing at his Moulton Paddocks yard.
The steroid stanozolol was found in a further seven animals, so raising the tally of horses under the trainer's control to have tested positive for doping to 22.
In a boost for Godolphin, whose stable was founded by the ruler of Dubai - Sheikh Mohammed bin Rashid Al Maktoum - in 1992, testing on nearly 200 horses at their other yard returned no positive results.
Trainer Saeed bin Suroor, who runs the Stanley House stable in Newmarket, will now take control of Moulton Paddocks, the yard formerly licensed to Al Zarooni.
"We welcome the news that Saeed bin Suroor's horses tested negative and this clears the way for him to now take charge of Moulton Paddocks," said Paul Bittar, Chief Executive of BHA.
In a statement posted on Godolphin's website, racing manager Simon Crisford said: "It is obviously very disappointing that seven further horses have tested positive for stanozolol.
"These results highlight why Sheikh Mohammed took the decision to lock down the stables at Moulton Paddocks until every Godolphin horse in training at Newmarket had been tested.
"All of Saeed bin Suroor's horses have tested clear and we are working with the BHA to put everything back in order at Moulton Paddocks."
The BHA said no further action will be taken against Al Zarooni, who has appealed the ban given to him in April and who says he was unaware that the use of anabolic steroids out of competition was banned in the United Kingdom.
The practice is allowed in Australia and Dubai, where Al Zarooni was based prior to taking control of Moulton Paddocks in 2010.
"We will not be taking any separate action in respect of these additional positive results whilst Mr Al Zarooni's appeal process is ongoing," said Adam Brickell, the body's Director of Integrity, Legal and Risk.
"In the meantime, the latest findings will form the subject of further interviews as part of the BHA's continuing investigation."
Following testing of 391 horses, the six to join Encke in British racing's most serious drugs scandal are his full brother Genius Beast as well as Energizer, Improvisation, Stamford, Steeler and Zip Top.
Like the other 15 to have previously tested positive, all the horses will be unable to compete for the next six months at the very least.
Both Godolphin and Al Zarooni can ask for the samples to be subjected to B sample analysis, with a decision to take up that option required by Thursday.
While no date has yet been set for Al Zarooni's hearing, which will take place no earlier than the last week of June, those in charge of the Godolphin stables must be hoping that the worst is now over.