Irish rider Denis Lynch has been forced to withdraw from the showjumping final in Hong Kong tonight after being provisionally suspended when his horse Latinus tested positive for a prohibited substance.
Doping control tests indicated the presence of capsaicin - a prohibited substance - in Latinus as well as three other horses from Germany, Brazil and Norway.
Lynch was notified earlier today by the International Equestrian Federation following receipt of the positive test result this morning.
"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.
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. A total of 15 jumping horses were tested.
There is potential implications regarding the team jumping medal results after Hansen's single penalty point had helped Norway secure bronze.
Capsaicin is a lotion or paste derived from the chilli pepper plant that when applied can have hypersensitizing - increasing a reaction to something - effects or act as a pain relief that, in both cases, can improve the performance of the horse.
It has always been an illegal substance but the technique to discover it's use has only recently been developed.
Analysis will now be carried out on the B-samples while evidence and written submissions will be requested from each of the riders before further action is taken.
"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."
With regards to the implications the case has on equestrian sports' involvement in future Olympics Holmberg added: "I wouldn't like to speculate. The International Olympic Committee will look at the sport from a broader perspective."
Lynch had been in eighth place ahead of the final having scored impressive rounds during qualifying, picking up just two penalty points after the first two rounds before recording six points in his third outing.
The 32-year-old's B-sample is expected to be analysed on Saturday.