The swimming portion of the triathlon event at the 2024 Paris Olympics might be impacted by poor water quality in the city’s Seine River. Tony Estanguet, president of the Paris 2024 Organizing Committee, said the water pollution is a challenge and the swimming event might be delayed until later in the games.

The triathlon plans were brought into question after a water charity released a report this week saying the water in the Seine showed alarming levels of bacteria like E.coli.

Surfrider Foundation Europe completed 14 tests on water samples taken from two spots on the river between September 2023 and March 2024 and found all but one showed poor water quality.

Olympic triathlons involve a .93-mile (1.5 km) swim, a 24.8-mile (40 km) bike ride, and a 6.2-mile (10 km) run. The Olympic event is set to take place on July 30 and 31, with athletes starting their swim at the Pont Alexandre III bridge. After swimming two laps, they will climb 32 stairs up to the top of the bridge again to begin the bike ride and then finish with the run.

Surfrider Foundation said in a social media post that the samples revealed high levels of pollution at the Alexandre III Bridge and that a “shadow looms over the quality of the water in the Seine River.”

The organization blamed rainfall and sewage malfunctions for the pollution and warned the bacteria could lead to infections such as staphylococcus. They urged stakeholders to take action before athletes dip into the river.

When asked about the E.coli problem, Estanguet told Sport Accord this week that they are working hard on it, the Guardian first reported.

“When we decided to have this competition in the Seine we knew it will be a big challenge but with the authorities, there is a big program of investment and, when we talk about legacy, this project is fantastic,” he said.

Estanguet added he is confident the event will be held in the Seine because they have contingency plans and can postpone the race due to rain since it is set to take place at the beginning of the Olympics.

“But there’s a risk. There’s always a risk,” he said. “I was an athlete. I attended [the] World Championships that were postponed because of floods. When you are in a sport where you rely on the natural conditions, you have to adapt. It’s part of the flexibility in my sport.”

A spokesperson for Paris 2024 told CBS News that the Surfrider Foundation samples were not taken during the summer and that the City of Paris has always been transparent that the conditions of the Seine are suitable for bathers in the summer – not winter. 

“Paris 2024 has every confidence in the ability of all those involved and the work undertaken to make the Seine swimmable by the summer of 2024,” the spokesperson said via email.

In a statement to CBS News, a spokesperson for the International Olympic Committee said they “understand additional works due to be completed as part of the local government’s wider effort to improve the water quality of the River Seine will contribute to the running of the Olympic Games open water swimming competitions.” 

The spokesperson added that they can change the schedule “to ensure the events can take place, so there is no reason to speculate.”

Paris had been cleaning up the Seine so people could swim in it again, but plans to hold a swimming event ahead of the Olympics were derailed due to a sewage problem. Still, French President Emmanuel Macron said he would take a dip once the river is cleaned, which the city says will happen by 2025.

The Paris 2024 spokesperson said the multi-agency effort to make the Seine swimmable was initiated more than 30 years ago. By the time the Games start, the efforts to clean up the river “will have reduced bacteriological pollution by 75%.”

Five Olympic events will take place in the Seine, the spokesperson said: men’s and women’s marathon swimming events and the men’s, women’s and mixed relay triathlon events. Eleven para-triathlon events will also be held in the Seine during the Paralympic Games.   

Last month, water pollution in another major European river almost derailed an athletic event. River Action, an environmental group, said sections of London’s River Thames had “alarmingly high” levels of E. coli and worked with organizers of the Oxford-Cambridge Boat Race to create guidelines for rowing in the water.

The annual boat race went on even though the group found E. coli levels up to 10 times higher than what is considered the worst category for public bathing by U.K. authorities.