It was so nearly the showcase equestrian Olympic Games that the International Equestrian Federation (FEI) and the Hong Kong Jockey Club had worked tirelessly to achieve. But two hours before the individual showjumping final - the final event - was due to start at the Sha Tin arena came the news that the organisers had dreaded.

Four horses, including two leading contenders for the individual contest - Tony Hansen's Camiro, a member of the bronze medal-winning Norway team, and Ireland's Latinus, belonging to Denis Lynch - had been ruled out of the competition after testing positive for Capsaicin, a prohibited substance under FEI rules.

Sven Holmberg, chairman of the FEI Jumping Committee, described the news as a “serious blow for the sport”. Although unwilling to speculate on equestrianism's future as part of the Olympic Games, he said: “We are aware of the implications which this can have and the fact that all four horses tested positive for the same substance makes it all the more serious.”

Capsaicin, which was also found in the German horse, Coster, ridden by Christian Ahlmann, and the Brazilian horse, Chupa Chup, ridden by Bernardo Alves (only 15 showjumping horses were tested), can give a sensation of burning - making a horse hypersensitive if it knocks a showjumping fence. It is also used for pain relief.

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Although banned by the FEI, it is only in the past two years that equipment has become sophisticated enough to test for it. Riders and team managers were all warned that the Hong Kong Jockey Club's laboratory, which tested the samples, had the most up-to-date facilities in the world.

Lynch, the only one of the four riders to speak in public about his suspension, said his horse's positive reading had come from a medicine, Equiblock, that he regularly used on Latinus to stop pain. He said he had not realised Capsaicin was forbidden. “I've been using it all year and my horse has been tested at several shows and never had a positive reading,” he said. Unrepentant, he claimed that his summary suspension by the FEI - automatic if an A sample is positive - had “robbed” him of the chance to go for gold.

Hansen's Camiro, who led the individual placings after the team contest, is the only horse that could affect the team medal placings if his suspension is upheld, but the outcome will not be known for several weeks. If Camiro's positive testing is upheld, Norway will lose the bronze medal to Switzerland. The doping scandal overshadowed the individual showjumping final, which provided its own sequel to the drama-filled day when it was won by the former cocaine user, Eric Lamaze, on Hickstead. Lamaze, 40, from Montreal, who won the gold after a jump-off with Rolf-Göran Bengtsson, of Sweden, riding Ninja, missed the 1996 Olympic Games in Atlanta after testing positive for cocaine.

Beezie Patten, of the United States, took the bronze medal on Authentic after a jump-off involving the seven horses who had finished the two rounds on four faults. Ben Maher, of Great Britain, on Rolette, who had gone into the final day as a leading medal contender after his three perfect earlier rounds, saw his Olympic dream crushed when Rolette, having been clear in the first round, visibly weakened in the sultry heat of the second round, just as Tim Stockdale's Corlato had done earlier, and collected 20 faults. “She's never done that before - it's bitterly disappointing,” Maher said, “Until now she has exceeded all my expectations.”