Canelo Alvarez has an explanation for why he tested positive for the banned substance clenbuterol.

Promoters for the middleweight boxer, who is set to have a rematch against Gennady Golovkin on May 5, are blaming contaminated meat for the traces of clenbuterol that turned up in two urine samples on February 17 and February 20, according to reports.

Both Alvarez and GGG had agreed to be randomly tested by the Voluntary Anti-Doping Association as part of the deal for their first fight, as well as the upcoming rematch. According to ESPN, clenbuterol has shown up in drug tests for many Mexican athletes in recent years because of meat contamination in the country.

"As part of the voluntary testing program that Canelo Alvarez insisted on ahead of his May 5 fight, one of his results came back positive for trace levels of clenbuterol, consistent with meat contamination that has impacted dozens of athletes in Mexico over the last years," Golden Boy Promotions, Alvarez's promoter, said in a statement per ESPN. "As Daniel Eichner, director of [the Sports Medicine Research and Testing Laboratory], the WADA-accredited lab that conducted the tests stated in his letter [Monday], 'These values are all within the range of what is expected from meat contamination.' Upon receiving this information, Golden Boy immediately notified the Nevada State Athletic Commission and Gennady Golovkin's promoter, Tom Loeffler."

Despite the positive test, the rematch is still on.

Alvarez, who has been training in his hometown of Guadalajara, Mexico will reportedly move his training camp to the United States and submit to additional tests, according to USA Today. "I am an athlete who respects the sport and this surprises me and bothers me because it had never happened to me," Alvarez said in a statement. "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."

The first match between Alvarez and GGG last September ended in a draw after one judge scored it 118-110 for Canelo, a second judge had it 115-113 for Golovkin and the third had it even.