Three German swimmers became ill after competing in the open water races at the Paris Olympics, though it was not immediately clear if the long-polluted Seine River was responsible for their sickness.

The swimmers were not identified in a statement released Saturday by the German Olympic Sports Confederation, though Leonie Beck went on social media to reveal her condition.

Beck, who finished ninth in the 10-kilometre event, posted a picture of herself on Instagram giving a thumbs up but looking ill.

"Vomited nine times yesterday + diarrhea," she posted, before adding sarcastically, "Water quality in the Seine is approved," accompanied by a check mark.

The German committee said in its statement that three of its athletes became ill.

"Two female German open water swimmers were treated as outpatients [Friday] for nausea, vomiting and diarrhea. They have been feeling much better since this morning," the statement said. "Another swimmer with similar symptoms is currently being treated by the German team doctors."

The other German swimmer in the women's open water race was Leonie Maertens, who placed 22nd in the 24-woman field.

Germany also had two swimmers in the men's event: silver medallist Oliver Klemet and eighth-place finisher Florian Wellbrock. It wasn't revealed which one was being treated.

Paris organizers and World Aquatics, the governing body for open water swimming, released testing figures that showed the water quality was well within the accepted limits deemed safe. There was a backup plan to move marathon swimming to the Olympic rowing and canoeing basin if the testing showed levels of E. coli and another form of bacteria exceeded those limits.

Concerns about the long-polluted Seine, where swimming had been banned for more than a century because of bacteria-laden waters, came to the forefront after Paris organizers announced plans to hold open water and the swimming portions of triathlon in the iconic river that runs through the heart of the French capital.

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Despite a massive, expensive cleanup project, some readings showed unacceptable levels of sickness-causing bacteria, leading to changes in the triathlon schedule and cancellation of one of two open water practice sessions scheduled ahead of the men's and women's 10-kilometre races.

Several athletes fell ill after the triathlon, but it wasn't clear if any of their conditions were caused by swimming in the Seine.

Though Beck clearly believes her illness was caused by the river, the German Olympic committee said the testing showed it was "feasible" to go ahead with the two races.

A total of 53 swimmers — 29 men and 24 women — competed in the open water races. Most said the cleanliness of the water was not an issue, with women's gold medalist Sharon van Rouwendaal of the Netherlands saying she actually took a few gulps of the river when she was feeling parched during her race.

"It was cold," she said. "It was nice."

Ireland's Daniel Wiffen, a swimming gold medalist in the 800-meter freestyle who competed in his first open water race, shrugged off concerns about the cleanliness of the waterway. He said the readings he saw ahead of the men's race showed less E. coli in the Seine than one would normally find in a pool.

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The Paris organizing committee issued a statement saying it had "heard reports of the athlete's illness and we wish them a speedy recovery."

"At this stage, we are not aware of any established link between the illness and the Seine's water quality," the statement said. "Water quality on the day of the marathon was considered `very good' or `excellent' across all four testing points and well within the thresholds established by World Aquatics."

World Aquatics deferred comment to Paris organizers.