Dillian Whyte has broken his silence over the positive anti-doping test ahead of his recent bout against Oscar Rivas, saying he was cleared to fight and won it "fair and square".
On Wednesday, the BoxingScene.com website reported that "one or more banned substances" had been detected in Whyte's A sample but neither Rivas nor the WBC was informed of the test.
The British heavyweight is understood to have returned the positive test, conducted by UK Anti-Doping, three days before Saturday's contest at The 02 in London, which Whyte won via a unanimous points verdict to claim the World Boxing Council's interim title.
The 31-year-old Londoner, who served a two-year doping ban between 2012 and 2014, did not respond to requests for comment on Thursday but has now issued a short statement on his Twitter feed.
"I am so disappointed with the rubbish that has been said about me over the last few days," he wrote.
"I have lawyers dealing with it and I have been told that I can't talk about it for good legal reasons. I was cleared to fight and I won that fight fair and square. Thanks for the support."
PA understands his lawyers have asked BoxingScene.com to remove the initial story, and their subsequent reports, on the grounds they are defamatory and an invasion of privacy.
Neither UKAD nor the WBC has made any comment on the matter, and the British Boxing Board of Control, the sport's national governing body, has only issued a short statement to say UKAD handles its anti-doping programme and it enforces any sanctions that may arise.
Whyte's promoter Eddie Hearn has commented, though, first via Twitter and then in a television interview.
On Wednesday, Hearn wrote that both Whyte and his Colombian opponent were "subject to extensive testing" by UKAD and the Voluntary Anti-Doping Agency, the Nevada-based organisation used by the WBC for its anti-doping programme.
Hearn added that "both fighters were cleared to fight by both bodies and the BBBofC".
On Thursday, Hearn told iFL TV that Whyte was cleared to fight by an "independent panel" and "a process was adhered to". He also asked fans not to rush to judgement, declaring him to be "absolutely broken".
But Rivas' promoter Yvon Michel has told reporters that nobody from their camp was aware of what was happening until the story broke in the media.
When athletes take drugs tests their blood or urine samples are split into A and B samples, with the latter being a smaller amount that is stored and usually only used to verify tests on A samples.
PA understands that only the A sample had been tested prior to the fight and Whyte, as is his right, asked for his B sample to be tested, a process he or a representative can attend.
If this second test confirms the first - and it almost always does - Whyte will most likely be given a choice between accepting a ban or proceeding to a hearing before the independent National Anti-Doping Panel.
If found guilty, he could expect an eight-year ban, although life bans can be given, depending on the circumstances of the case.
Earlier on Friday, WBC heavyweight champion Deontay Wilder, the man Whyte wants to fight next, told Talksport he would be "furious" if an opponent's positive test had been kept from him before a fight.
He said he thought Whyte and the British authorities could face a "massive lawsuit" if Whyte ends up being sanctioned.