VADA informed all relevant parties Wednesday that Jaime Munguia’s A-sample returned an adverse analytical finding for exogenous origin of testosterone metabolites following a urine sample on May 4 in Riyadh, Saudi Arabia, when he defeated Bruno Surace, sources told The Ring.

Munguia (45-2, 35 KOs), who denied doping in a statement released on via social media account Thursday afternoon, has 10 days to request analysis of his B-sample for exogenous origin of testosterone metabolites. If his B-sample also returns an adverse finding for the banned substance, Munguia faces suspension and the result of his decision victory could be overturned to a no-contest.

"Several experts have explained that there are multiple ways contamination can occur," Munguia's statement said. "I am fully willing to undergo any retroactive, current, or future testing to demonstrate that I have always been a clean athlete."

Mexico’s Munguia, 28, defeated Surace in the super middleweight rematch after he was KO'd in Round 6 by the Frenchman in December in The Ring’s Upset of the Year.

“I’m shocked by the news that Jaime Munguia tested positive for a banned substance,” Surace, 26, told The Ring on Thursday. “There’s no place in boxing for cheating; the sport is dangerous enough already.

“I went to Mexico and knocked out Munguia fair and square in December and I was gracious enough to give him a rematch in May. He knew he could not beat me on a level playing field. I trust that this result will be overturned immediately.”

Surace (26-1-2, 5 KOs) was a major underdog when he traveled to Tijuana, Mexico, in what amounted to a stay-busy fight for Munguia. After all, Surace was moving up one weight class and had scored just four career KOs.

In a career-defining victory, Surace sprung the upset when he landed a massive right hand that planted Munguia on the canvas in Round 6 for the 10 count.

Munguia linked up with renowned trainer Eddy Reynoso ahead of the rematch and held training camp in the Sierra Nevada mountains alongside former foe Canelo Alvarez. (Alvarez defeated Munguia in May 2024.)

And then on the undercard of Canelo’s victory over William Scull in May, Munguia exacted revenge with a unanimous decision victory over Surace in a competitive fight. Following the fight, Munguia climbed to No. 5 in The Ring’s 168-pound rankings while Surace fell to No. 8.

But now, that victory could be eliminated as Munguia faces discipline following a rocky 2024 where he suffered the first two losses of his career.

"Throughout my boxing career, I have undergone numerous anti-doping tests and have never tested positive," Munguia's statement said. "I was tested twice during this training camp, and both results came back negative, which is why receiving this notification of an adverse finding has been a complete surprise to me."