Seven further horses trained by banned Mahmood Al Zarooni, including 2012 St Leger winner Encke, have tested positive for anabolic steroid stanozolol, the British Horseracing Authority said in a statement on Monday.
Godolphin trainer Al Zarooni was handed an eight-year ban by the BHA last month for doping horses with anabolic steroids after 11 tested positive at his stable in Newmarket, England.
Al Zarooni, who admitted administering prohibited substances to four others, has appealed against the severity of the ban.
Following Al Zarooni's disciplinary hearing, the BHA conducted tests on all Godolphin-owned horses in training in Newmarket.
Blood samples were taken from 391 horses at the stables of Al Zarooni and Saeed bin Suroor, who also trains for Godolphin owner and Dubai ruler Sheikh Mohammed bin Rashid Al Maktoum in the town best known as the headquarters of British flat racing.
All of the horses under Bin Suroor's care tested negative, clearing the way for him to take charge of Al Zarooni's Moulton Paddocks stable, subject to BHA clearance.
The BHA said in a statement that no separate action would be taken "in respect of these additional positive results whilst Mr Al Zarooni's appeal process is on-going". No date has been set for the appeal.
"These test results endorse the swift action and measures taken by the BHA in this matter," said BHA chief executive Paul Bittar.
"Whatever the outcome of his appeal before the independent Appeal Board, the gravity and scale of the infringements warranted Mahmood Al Zarooni being removed from control of the yard as quickly as possible."
The scandal has caused serious embarrassment to Sheikh Mohammed. The BHA accused Emirati Zarooni of "deliberately flouting" the rules and a "widespread systematic misuse of illegal substances".
Al Zarooni, appointed Godolphin's second British-based trainer in 2010, won the Dubai World Cup - the world's richest horse race - in March last year and followed up by landing the prestigious St Leger with Encke at Doncaster in September.
The BHA said Encke, who has not raced since the St Leger, had tested negative after the race.