KINGSTON, Jamaica (AP) — A Jamaican who competed in taekwondo at the London Olympics said Tuesday he has tested positive for a banned substance.

Kenneth Edwards said he was notified a month ago about the diuretic and is awaiting results of a backup sample. A diuretic reduces body fluids and can mask drug use. He added he has not competed since July.

“I remain committed to being a professional athlete and would not do anything to compromise that position,” he said in a statement. “I have every intention of challenging these findings.”

Jason McKay, captain of Jamaica’s combined martial arts team, said he supports Edwards.

“From what we understand, a diuretic has appeared in his sample, which we are sure must be a mistake of some sort because, apart from his unquestionable honesty and integrity, there is no practical reason for him to be taking a diuretic, or any masking agent, when not competing,” he said.

The announcement comes as the world’s anti-doping authority launches a sweeping audit of Jamaica’s drug-testing agency amid allegations of inconsistent testing. WADA officials expect to visit the Caribbean island at the end of this year or the beginning of 2014.

Doping investigations also are under way involving other Jamaicans, including sprint stars Asafa Powell and Sherone Simpson. An anti-doping panel also publicly warned Veronica CampbellBrown for a violation, but she has been cleared to resume competition.