A South Korean coach has blamed the waters used during a Rio 2016 sailing test event for making his athlete ill.
Windsurfer Wonwoo Cho was taken to hospital during the event, with Danny Ok claiming the cause was "probably from the water" at Guanabara Bay.
Cho returned to competition a day later and finished 14th out of 28 - his second best finish of the regatta.
Rio 2016 organisers said: "There is no direct evidence to suggest the illness was caused by contact with water."
The statement added: "From a field of 326 athletes and 68 technical officials on the water, the International Sailing Federation (Isaf) medical team has received only two medical cases over the first five days of competition.
"Isaf have confirmed this number is significantly below the average for a regatta of this size. From a field of 326 athletes it is normal for some athletes to experience illness when travelling and competing in new environments."
In July, International Olympic Committee president Thomas Bach said cleaning up the polluted Guanabara Bay - the venue for the Olympic sailing and windsurfing competitions - remained a serious challenge.
Sailors in the area have reported seeing pollution, including furniture and floating animal carcasses, while nearly 70% of sewage in the Brazilian city is spilled raw into its waters.
Bach said some measures to clean the waters had already started, while others "will be applied to the bay just before the Olympics to make sure there is the safety and the health of the athletes".
The authorities in Rio initially promised that 80% of the bay would be cleaned up in time for the Games, which get under way on 5 August 2016.
But they have admitted more recently that those targets would not be met.
Earlier this month United States rowing officials refused to blame the water when 15 junior team members fell ill at a test event.