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British heavyweight contender Dillian Whyte has tested positive for a banned substance, according to a report from Thomas Hauser of Boxing Scene

Hauser reports that Whyte tested positive for one or more banned substances on July 17, just three days before his bout with Oscar Rivas to determine the next mandatory challenger for Deontay Wilder's WBC title. The British Boxing Board of Control, as well as Whyte's promoter, Eddie Hearn, were notified prior to Saturday's fight, but the BBBC allowed the fight to go on as scheduled, according to the report.

Despite getting knocked down by an uppercut in the ninth round, Whyte defeated Oscar Rivas in London by a unanimous decision, with the judges scoring the fight 115-112 (x2), 116-111. With the victory, he became the mandatory challenger for Deontay Wilder's WBC heavyweight title. 

That was an important milestone for Whyte (26-1, 18 KOs), who has long complained of being avoided by the top heavyweights in the world. 

"Deontay Wilder has ducked once again," Whyte wrote earlier this year in a column for TalkSport. "If people don't believe he's running from the big fights by now, then I don't know what to tell them... I want Wilder bad, especially after all of this nonsense. After all the time I've spent chasing the WBC belt, I want that above all else."

There was still no guarantee Whyte would ever get a chance to fight Wilder, who has already announced a rematch with Luis Ortiz for later this year, and is expected to take on Tyson Fury in a rematch of their instant classic in early 2020. And besides, boxing commissions are quite adept at delaying and preventing mandatory challenges from taking place. At the very least, however, Whyte's win would have gotten him closer to his goal of a title fight with Wilder. 

Wilder responded to the report in true Wilder fashion with a lengthy post on Instagram.

That he reportedly tested positive before the bout with Rivas only further complicates things for Whyte, and makes it less likely that he'll ever get that fight with Wilder. 

Whyte's promoter, Eddie Hearn, issued a statement on Twitter regarding Boxing Scene's report. 

"Further to reports I can confirm that both Dillian Whyte and Oscar Rivas were subject to extensive VADA and UKAD testing for their bout," Hearn wrote. "Both fighters were cleared to fight by both bodies and the BBBofC."

This is not the first time that Whyte has been the subject of banned substances. In 2012, he was suspended from boxing for two years after testing positive for Methylhexaneamine. He appealed that suspension, but it was upheld and he returned to the ring in 2014.