One of the most anticipated boxing rematches in recent history is now under threat.

The Canelo Alvarez versus Gennady Golovkin rematch scheduled for May 5 in Las Vegas is now swinging precariously in the wind after Alvarez tested positive for trace levels of the banned substance Clenbuterol in a routine pre-fight drug test. The fight is still two months away, and Alvarez’s team is now scrambling to do damage control.

Golden Boy promotions have alerted the Nevada State Athletic Commission of the failed test, but also claim the trace levels are due to contaminated beef that Alvarez consumed in Mexico. Here is their full statement, including a direct quote from Alvarez himself, as well as the lab director where the positive test was confirmed:

Alvarez announced he would immediately move his training camp from Mexico to the United States, to avoid a repeat contamination. The lab director also confirms that the trace amounts are within the range you expect from tainted food, and hopefully not in line with the expected range of a doping athlete.

The Nevada State Athletic Commission will have to make a decision on what to do here, as the fight is currently still scheduled to go down on May 5. The first meeting with Alvarez and GGG ended in a controversial draw in September 2017.