Jamaican sprinter Asafa Powell has confirmed that he tested positive for a banned stimulant at national trials last month.

The former 100m world record holder was found to have oxilofrine (methylsynephrine) in his system, and although he accepts responsibility, he insists that he is not a cheat.

"I will confirm that a sample I provided at national trials in June earlier this year has returned adverse findings," read a statement from the 30-year-old.

"I want to be clear in saying to my family, friends and most of all my fans worldwide that I have never knowingly or willfully taken any supplements or substances that break the rules. I am not now - nor have ever been - a cheat.

"My team has launched an investigation and we are cooperating with the relative agencies and law enforcement authorities to discover how the substance got in my system."

Powell went on to add that the positive test means that he will no longer be able to compete for his country at the upcoming World Championships in Moscow.

"This result has left me completely devastated in many respects," he added.

"Professionally, this finding fully negates any possibility of me being apart of Jamiaca's contingent of athletes competing at the World Championships in Moscow later this summer.

"I accept the consequences that come with this finding - after all, there is only one Asafa Powell. My fault here, however, is not cheating but instead of not being vigilant."

Compatriot and 2006 Commonwealth 100m champion Sherone Simpson was also found to have oxilofrine in her system.

Meanwhile, news that American sprinter Tyson Gay tested positive for a banned substance broke earlier today.