Alexander Besputin was notified by the Monaco Boxing Federation of an ''abnormal test result'' in the wake of his victory over Radzhab Butaev on Nov. 30, which was contested for a version of the WBA welterweight.
The two met in Monte Carlo in what was a fast-paced affair that saw Besputin win by scores of 116-112 on all three judges' cards.
According to the drug test report, a copy of which was obtained by ESPN, the substance that triggered the positive result is LGD-4033 (Ligandrol), commonly used by body builders because of its ability to produce lean body mass while lowering body fat.
Both Besputin and Butaev came in below the 147-pound weight limit for their fight.
According to the United States Anti-Doping Agency website, Ligandrol "is prohibited under class S1.2 Other Anabolic Agents on the WADA Prohibited List. LGD-4033, and all SARMs, are prohibited at all times for all athletes, both in and out of competition."
"I am not surprised at all at hearing this news, and that's why I was never respectful of him as an athlete or as a person," Butaev said in a statement. "Ahead of the fight my team insisted on VADA testing while he and his team were denying it all along, and even after I agreed to pay for both sides, including his costs, he was very reluctant. After finally enrolling he attempted to ignore the requests from VADA for two weeks for his whereabouts to be tested.
"This is a disgrace and is disrespectful to the sport of boxing. All I have been wanting is a rematch since the final bell of the first fight.
"Now with a level playing field I'm even more confident in a victory!'" he continued.
Besputin, 28, is represented by Top Rank.
Carl Moretti, Top Rank's vice president of boxing operations, told ESPN early Tuesday evening, "We are aware of the situation, we are discussing it thoroughly with his team. Other than that, we have no further comment."
The Nov. 30 card was promoted by Matchroom Sports, which was made aware of the findings Monday.
"It's been sent to the WBA, who I understand are dealing with it," said Matchroom Boxing promoter Eddie Hearn.