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Irishman Denis Lynch has been forced out of the Olympic show jumping final after his was one of four horses banned for doping.
The International Equestrian Federation (FEI) announced that four of the horses taking part in Hong Kong had testing positive for banned substances.
The presence of capsaicin was found in tests from Lynch's horse Lantinus, along with horses from the Brzil, Germany and Norway teams.
"The FEI provisionally suspends all competitors who test positive in doping or positive medication cases at the Olympic Games in the interests of the integrity of the sport," read a statement from the FEI.
"Capsaicin is classified as a 'doping' prohibited substance given its hypersensitising properties, and as a 'medication class A' prohibited substance for its pain relieving properties."
The horses which also took part in the team competition have also been disqualified from that and it could affect the medals that were handed out, although with Great Britain finishing down in seventh they would not be affected.
The three other riders suspended were Germany's Christian Ahlmann, on Coster, Brazil's Bernado Alves, on Chupa Chup, and Norway's Tony Andre Hansen on Camiro.
"This is certainly a serious blow to the sport," Sven Holmberg, chairman of the FEI jumping committee told a press conference.
"We are aware of the potential implications this has for equestrian sports and showjumping.
"The seriousness of this case is increased because four horses have tested positive for the same substance."
