Canelo Alvarez tested positive for trace levels of the banned substance clenbuterol on February 17 and on February 20, but he was clean in two tests since then.

THE RING’s middleweight champion blamed the positive result on contaminated meat consumed in Mexico, and the director of SMRTL, the World Anti-Doping Agency-accredited lab that collected the samples said Monday “these values are all within the range of what is expected from meat contamination.”

Alvarez (49-1-2, 34 knockouts) was tested again by the Voluntary Anti-Doping Association (VADA) on March 3 as well as on Monday, and both urine specimens collected revealed no traces of any banned substances in his system, a source told THE RING. Nevada State Athletic Commissioner Bob Bennett confirmed that Alvarez’s results were negative for any banned substances on those dates.

The commission is conducting an investigation ahead of Alvarez’s highly anticipated May 5 rematch against Gennady Golovkin, set for T-Mobile Arena, and part of that process will be to ensure Canelo stays clean.

With the substance now out of his system, it’s expected the fight will go ahead as planned, eight months after Canelo and Golovkin fought to a controversial draw.

“I am an athlete who respects the sport and this surprises me and bothers me because it had never happened to me,” Alvarez said Monday. “I will submit to all the tests that require me to clarify this embarrassing situation and I trust that at the end the truth will prevail.”

Clenbuterol is a performance-enhancing substance used by athletes, mainly as a fat burning tool. The substances helps increase muscle mass and reduce body fat, and is classified as an anabolic agent because it promotes muscle growth through anabolic properties.

However, the substance is also often found in meat in Mexico, where food regulations are far less strict (clenbuterol is banned in the U.S.). Erik Morales tested positive for clenbuterol ahead of his rematch with Danny Garcia in 2012, and more recently, so did Mexican 130-pound contender Francisco Vargas prior to his 2016 WBC title fight against Orlando Salido. Zilpaterol, a substance similar to clembuterol and used to increase the size of cattle, was found in Mexican bantamweight contender Luis Nery’s system after he knocked out WBC/RING champ Shinsuke Yamanaka last year. All three fighters blamed meat consumed in Mexico.

“Of course, I still want to fight,” Golovkin told THE RING on Wednesday at The Summit gym in Big Bear, California, where he trains. “I’m a fighter and I have unfinished business with Canelo.”

Mike Coppinger is the Senior Writer for RingTV.com. Follow him on Twitter: @MikeCoppinger