WBA heavyweight champion Lucas Browne has failed a drugs test.
The Australian won the title earlier this month by beating defending champions Ruslan Chagaev in Russia.
Browne tested positive for a sample of clenbuterol, his management has revealed.
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Clenbuterol is a powerful drug that is often used to treat asthma. It can also help build up lean muscle mass and burn off fat.
The drug can be digested by humans accidentally in some forms of beef but anti-doping rules state that the slightest trace in an infringement.
After being found guilty, Browne said:
"I would like to assure all fans, the whole of the boxing world and all of Australia that I am not a drug user or a drug cheat," said Browne, per BBC.
"I will fight for as long as it takes to clear my name. I have never heard of the drug clenbuterol and had no idea what it is used for.
"I am now aware that it is essentially a weight-stripping drug and as a heavyweight boxer, the idea of me using it is utterly ridiculous.
"My team and I were well aware of the many risks involved in going to a place like Chechnya to fight a reigning champion and believed we had taken sufficient precautions.
"In addition, it was at our insistence that Vada [Voluntary Anti-Doping Association] testing was implemented for the fight," he concluded.
During the fight against Uzbekistan’s Chagaev, Browne was knocked down in the sixth round but recovered to extend his record to 24-0.
The news comes just weeks after Maria Sharapova revealed she failed a drugs test at the Australian Open.
The Russian tested positive for meldonium, a substance she has been taking since 2006.
"I did fail the test and take full responsibility for it," said Sharapova, who won Wimbledon as a 17-year-old in 2004.