The fate of the the rematch between Saul “Canelo” Alvarez and Gennady Golovkin is in jeopardy after the Nevada Athletic Commission (NAC) filed an official complaint against Alvarez Thursday.

NAC executive director Bob Bennett said in a statement that the organization filed a complaint against Alvarez following the completion of its investigation into his two failed drug tests, according to MMA Fighting.

“After completing my investigation, I made the determination to file a complaint against Mr. Alvarez and set the matter for a disciplinary hearing during the Commission’s regularly scheduled meeting on April 18th,” Bennett wrote. “Therefore, I am cancelling the hearing that was scheduled for Friday, March 30th.”

The Alvarez-Golovkin rematch, scheduled for May 5, in Las Vegas now hangs in the balance. Their fight last September ended in a split draw. Alvarez first tested positive for the banned substance clenbuterol during a test issued by the Voluntary Anti-Doping Association, which was part of his rematch deal with Golovkin. The NAC responded by temporarily suspending Alvarez on March 23.

However, George Willis of the New York post reports that the World Anti-Doping Agency said the levels of clenbuterol present in Alvarez’s blood test were minute and completely consistent with an outbreak of meat contamination that’s been seen numerous athletes in Mexico in recent years.