(CNN) -- The equestrian competition at the Beijing Olympics has been hit by a major doping scandal involving four horses and their riders, including a bronze medal winner.
Norway's Camiro, ridden by Tony Andre Hansen, competes in the team jumping event.
The test results were announced by the sport's international governing body -- just ahead of the individual show jumping competition in Hong Kong, won by Eric Lamaze of Canada.
The four horses were found to have been given capsaicin, a substance prohibited because of its pain-relieving properties.
The horse Camiro, ridden by Tony Andre Hansen, was part of Norway's bronze-medal line-up in the team show jumping.
The other three horses are Ireland's Lantinus, ridden by Dennis Lynch; Brazil's Chupa Chup, ridden by Bernardo Alves; and Germany's Coster, ridden by Christian Ahlmann.
Hansen, Lynch and Alves were not allowed to ride in the individual competition. Ahlmann was not entered in the event.
A second blood sample for each horse still must be tested and if the results are the same there is likely to be a re-allocation of the medals in the team show jumping where the United States won gold, Canada the silver and Norway the bronze.
Switzerland, who finished fourth, would likely benefit from any disqualification. It is the second successive Olympics where doping has cast a shadow of proceedings in the show jumping.
Germany were stripped of the team gold in Athens after the horse ridden by Ludger Beerbaum, who is competing in Hong Kong, was disqualified after testing positive for doping.
Meanwhile, Lamaze rode Hickstead to take individual gold in a timed jump-off with Rolf-Goran Bengtsson of Sweden on Ninja, who took the silver. American rider Beezie Madden on Authentic won the bronze.
Lamaze and Bengtsson were among 10 riders with clean rides in the first rounds, but they were the only ones to cleanly finish the second round. Bengtsson knocked down one rail in the jump-off, while Lamaze went clean to win the gold.
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