LONDON (Reuters) - Newmarket-based trainer Gerard Butler faces charges of administering banned anabolic steroids to nine of his racehorses in training, the British Horseracing Authority said on Friday.

The BHA detailed the charges in a statement on its website with the date of a disciplinary hearing still to be confirmed

Butler said in April - after Godolphin trainer Mahmood Al Zarooni had his licence revoked for eight years for doping racehorses - that medication containing stanozolol had been given to several horses at his stables on veterinary advice.

He said then, in an interview with the Independent newspaper, that he had been "advised in good faith" by his vets and believed the product did not breach the rules.

Butler added that he had been told the medication, known as Sungate and used to treat injured joints, may have been prescribed to as many as 100 racehorses in Newmarket.

The BHA said samples taken from nine of his horses on Feb 20 had tested positive for stanozolol.

The charges against Butler also included administering intra-articular injections to several horses despite not being a qualified or registered vet.

The BHA said a wider investigation into the use of Sungate remained ongoing and several trainers had been spoken to.