Tyson Fury has denied claims of doping as his controversial career was cast into the spotlight again.
A report by the Sunday Mirror alleged traces of a banned substance were discovered in a sample taken from the world heavyweight champion last year. Fury's promoter Hennessy Sports has denied the allegations.
A statement read: "We are baffled by today's story in the Sunday Mirror. Tyson Fury absolutely denies any allegation of doping. He looks forward to recovering from his injury and defending his titles against Wladimir Klitschko in October."
UK Anti-Doping (UKAD) - which the Sunday Mirror reported was overseeing the investigation - spokeswoman Sophie Ashcroft said: "UK Anti-Doping does not discuss or disclose details of any cases until due legal process has been completed or a respondent chooses to put the information into the public domain.
"This is to protect the rights and privacy of all involved and to ensure that a case is not subjected to unnecessary prejudice.
"It is important to note that an anti-doping rule violation is only deemed to have been committed once the legal process, including any appeals, has been completed. At that point, details of a violation will be made available on the UKAD website."
The doping allegations are the latest controversy in a career which has frequently attracted negative publicity.
In the build-up to November's defeat of Klitschko - which remains among the finest any British fighter has secured - he expressed extreme views on homosexuality and paedophilia.
He had told The Mail on Sunday: "There are only three things that need to be accomplished before the devil comes home: one of them is homosexuality being legal in countries, one of them is abortion and the other one's paedophilia."
Shortly after that victory, which he helped promote by dressing up as Batman, he was accused of sexism when revealing his belief that "a woman's best place is in the kitchen and on her back".
Police also investigated a hate crime allegation against Fury, when the strength of feeling towards him was so strong there were protests at his presence at the BBC's Sports Personality of the Year awards, where he apologised.
Since that apology, however, he has sparked further outrage when in an hour-long video posted last month he made homophobic, sexist and anti-Semitic remarks while being outspoken on rape and bestiality.
The Campaign Against Anti-Semitism called for him to be banned for his "offensive and racist remarks" and made a complaint to the British Boxing Board of Control (BBBofC). Klitschko earlier this week compared his views to those of Nazi leader Adolf Hitler.
The BBBofC has previously sanctioned the WBA and WBO heavyweight champion. They fined him £3,000 for abusing fellow fighters David Price and Tony Bellew as "gay lovers" on Twitter in 2013.
That was before a further fine of £15,000 and a misconduct charge in 2014 for his behaviour and foul-mouthed language at a press conference promoting his fight with Dereck Chisora, as well as the driving ban issued in June 2015.
After admitting driving at 90 miles per hour in southern Scotland, he spent a weekend in police custody after failing to appear personally in court. He received a two-month ban and a £400 fine for the offence.