Nine trainers have escaped disciplinary action over the use of a veterinary product which includes an anabolic steroid on 43 horses, the British Horseracing Authority said in a statement on Wednesday.
The trainers were cleared after an investigation found that the Sungate treatment, which is used on horse joints, was administered on the advice of and by veterinary surgeons.
The investigation started after nine horses in the yard of Newmarket trainer Gerard Butler failed testing in February.
He is still facing seven disciplinary charges, including giving injections to horses despite not being a qualified or registered vet.
Trainer Al Zarooni, an employee of Dubai ruler and Godolphin owner Sheikh Mohammed bin Rashid al-Maktoum, was banned by the BHA for eight years in April for administering banned anabolic steroids to 22 horses based in Newmarket.
(Reporting by Josh Reich; Editing by Mark Meadows)