Belgium has forfeited from the mixed relay triathlon after one of its team athletes fell ill, the country’s Olympic team confirmed in a Sunday press release. 

Claire Michel, who participated in the women’s triathlon and swam in the Seine River on Wednesday, has withdrawn from the meet because of her illness. Belgian newspaper De Standaard claimed that Michel was infected with E.coli. TIME is out to Team Belgium for comment. 

The water quality of the Seine has been subject to intense scrutiny after French officials announced it would be used for a number of Olympic events, despite a swimming ban that’s been in place because of water pollution since 1923. Organizers invested some $1.5 billion to help clean up the iconic river, prompting French President Emmanuel Macron to promise he would swim in the Seine to highlight its cleanliness. Anne Hidalgo, mayor of Paris, swam in a cleaned-up Seine just nine days before the opening ceremonies, which also took place on the river.

Although officials remained adamant that water quality levels would meet the mark, in July, water testing still displayed levels of bacteria, including E.coli and enterococcus, at unsafe levels. The Seine also failed to reach the World Triathlon’s water standards for swimming during the Olympics, causing the postponement of the men’s triathlon and athletes’ training sessions, including one for the upcoming triathlon on Monday. Team USA triathlete Seth Rider even jokingly said that he was intentionally exposing himself to E.coli prior to the July 31 race.

To win the triathlon, athletes must tackle a 300m swim, 7km bike ride, and 1.8km run. The women’s and men’s individual triathlon took place on July 31, but the mixed relay is slated for Monday, Aug. 5.

Belgium won bronze at the Paris test event for the mixed relay in 2023. “The BOIC and Belgian Triathlon hope that lessons will be learned for future triathlon competitions,” said Team Belgium. “We are thinking of training days that can be guaranteed, competition days and formats that are clear in advance and circumstances that do not cause uncertainty among athletes, entourage and fans.”