Champion jockey Oisin Murphy has tested positive for cocaine and says he will "fight to clear my name".
The 25-year-old Irishman denies taking the drug and says he is awaiting the result of a B sample following the test in France in July.
Murphy, who is number one jockey for Qatar Racing and on course to retain his championship, faces a six-month ban if he is found to have taken the drug.
He said subsequent hair tests have found no trace of the substance.
"I have never taken cocaine in my life and I will do everything that I can to prove that I have not taken cocaine," he said.
"I want to thank those who are supporting me and in the meantime I want to keep riding winners and focus on my career."
The jockey enjoyed a landmark success in June when winning the 2,000 Guineas at Newmarket aboard Kameko, trained by Andrew Balding.
He returned the positive test in a urine sample at Chantilly Racecourse on 19 July but has been allowed to continue riding while further investigations take place.
Murphy said he learned via text message from France Galop - when he was in York for the Ebor meeting on 19 August - that his A sample had metabolites of cocaine. He organised for an independent laboratory to undertake hair tests, which were negative.
"I had to release a statement earlier today as the story had got round, and also it's a weight off my shoulders," he told Racing TV on Thursday.
"I've been riding to the best of my ability - I had a great week last week - but something needed to be said today and I'm pleased it's out there.
"I am innocent and I think the people closest to me believe in my innocence, and I've been able to push it out of my head.
"I don't come into contact with drugs. I didn't ever expect to hear from France Galop, the BHA or wherever I ride around the world. I don't take even painkillers. I have an inhaler and that's about it."
Murphy, who is due to have four rides at Chelmsford's evening meeting on Thursday, leads the 2020 Flat Jockeys Championship with 111 winners - 13 ahead of nearest rival William Buick.
A British Horseracing Authority spokesperson said: "We have been made aware that there is an ongoing anti-doping matter in France in relation to Oisin Murphy which is currently the subject of further analytical investigation.
"We will continue to liaise with the Professional Jockeys' Association and France Galop and assess any new information as it becomes available."
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