Saul Alvarez has tested positive for trace levels of Clenbuterol ahead of his rematch with Gennady Golovkin in May, according to Golden Boy Promotions.
But after attending a voluntary drugs test before his rematch with multiple world middleweight champion Gennady Golovkin, the results have been attributed to meat contamination.
"As part of the voluntary testing programme 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," read a statement from Golden Boy Promotions.
"As Daniel Eichner, director of SMRTL, the WADA-accredited lab that conducted the tests stated in his letter (on 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."
Golden Boy promotions said Alvarez will immediately move his training camp from Mexico to the United States and will submit to any number and variety of additional tests.
The promoters added Alvarez has tested clean dozens of times over the course of his previous 12 fights.
Alvarez said: "I am an athlete who respects the sport and this surprises me and bothers me because it had never happened to me.
"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."