Luis Ortiz fails drugs test before his Deontay Wilder fight in November
Luis Ortiz has failed a drugs test before his heavyweight clash against Deontay Wilder, says World Boxing Council president Mauricio Sulaiman.
Cuban Ortiz, 38, was due to challenge WBC champion Deontay Wilder for his title in New York on 4 November.
Sulamain said on Twitter the Voluntary Anti-Doping Association had confirmed Ortiz tested positive for a banned substance but gave no further details.
Promoter Lou DiBella said the Ortiz-Wilder fight is set to be called off.
"As of now the fight isn't cancelled but it's difficult to see it going ahead," DiBella told BBC World Service.
"Deontay will be very disappointed with the news. It is one of the biggest fights of his career potentially down the drain."
American Wilder, 31, has won all 38 of his professional fights, while Ortiz is unbeaten in 27 bouts.
Ortiz, nicknamed 'King Kong', was a contender to challenge for British boxer Anthony Joshua's WBA title.
The winner of the Ortiz-Wilder bout could have faced him should Joshua beat Kubrat Pulev in December.
Ortiz was previously banned for eight months after testing positive for the banned steroid nandrolone in 2014.