Anthony Joshua's next opponent Jarrell Miller has returned an "adverse finding" in a drug-testing sample, says Joshua's promoter Eddie Hearn.
American Miller, 30, is due to fight Briton Joshua, 29, at Madison Square Garden in New York on 1 June.
Joshua is scheduled to defend his IBF, WBA and WBO heavyweight titles against the undefeated Miller, who has never fought for a world title.
Hearn said Joshua's "preparations continue" for his US debut.
Hearn said he had been informed by the the Voluntary Anti-Doping Association (Vada) about the finding from a sample collected on 20 March. Vada operates within boxing and mixed martial arts
Jarrell Miller: Anthony Joshua's next opponent returns 'adverse finding' in sample
American Miller, 30, is due to fight Briton Joshua, 29, at Madison Square Garden in New York on 1 June.
Joshua is scheduled to defend his IBF, WBA and WBO heavyweight titles against the undefeated Miller, who has never fought for a world title.
Hearn said Joshua's "preparations continue" for his US debut.
Hearn said he had been informed by the the Voluntary Anti-Doping Association (Vada) about the finding from a sample collected on 20 March. Vada operates within boxing and mixed martial arts
Jarrell Miller: Anthony Joshua's next opponent returns 'adverse finding' in sample