No charges will be brought against trainers interviewed during a British Horseracing Authority investigation into the use of the veterinary product Sungate.

Sungate contains stanozolol, an anabolic steroid and therefore a prohibited substance under the Rules of Racing.

The BHA spoke to a number of trainers as the treatment was advised by a veterinary practice which all had in common.

The investigation identified that 43 horses from nine trainers had been treated with Sungate since early 2010.

However, all had been correctly entered into the relevant medical records and had been administered by veterinary surgeons and on veterinary advice, and with none of the horses producing positive samples, the BHA concluded there were no grounds for charges to be brought.

Newmarket-based trainer Gerard Butler went public over the issue of Sungate in the wake of the Mahmood Al Zarooni inquiry in April at which the trainer was disqualified for eight years after being found guilty of administering anabolic steroids to 15 horses in his care.

The BHA has been keen to point out that although Sungate contains stanozolol, it is in fact used to treat joints which makes it different from an intramuscular anabolic steroid product which would have a much higher concentration of anabolic agent.

The BHA said it became aware of the situation following a visit to Butler's yard in February as part of its testing in training programme, from which nine tested positive for stanozolol.

On investigation it became apparent that a veterinary practice, which had imported the drug legally from Italy, was prescribing Sungate and recommended it for horses in training, the BHA said.

After meeting with the vets the BHA said it was clear Butler was not the only trainer to have used the treatment and the authority met with 38 trainers who used the same vets.

Butler does face charges as he admitted to administering the drug himself in some cases and is not a qualified vet. The date of the hearing has still to be announced.