PARIS – The men’s triathlon race, which will take place on Tuesday morning, has been delayed by a day because of unsafe water pollution levels in the Seine River, Olympic organizers said.

But the International Olympic Committee and World Triathlon, the sport’s governing body, said on Tuesday that tests taken in the morning “revealed water quality levels that did not provide sufficient guarantees for the event to be held.”

Officials blamed “meteorological events beyond our control” for the delay, citing the rain that fell on Friday (the day of the opening ceremony) and Saturday.

While water quality had improved since then, readings at some points on the swim lane remained above acceptable levels, they said.

The men’s race is now scheduled for Wednesday morning, a few hours after the women’s triathlon.

To clean up notoriously dirty Seine has been a decades-long goal, dating back to the 1990s. The effort accelerated after Olympic organizers announced plans to hold triathlon and long-distance swimming events in the Seine. The French government has invested more than $1.5 billion in the effort over nine years.

Heavy rains overwhelm the city’s antiquated sewage system, leaking raw sewage into the Seine and increasing the speed of E. coli bacteria.

The waters have been tested daily and met purity standards in the days leading up to the games. Less than two weeks ago, The mayor of Paris took a dip in the Seine to demonstrate water safety.

Marisol Casado, president of World Triathlon, said at a press conference that the organization prioritizes the athletes’ health and said she was confident the rescheduled competition would go ahead on Wednesday.

The organizers have set aside Friday as a reserve day for the triathlon competition in case of another delay.

If river water quality continues to fall below standard, organizers have suggested postponing the swimming portion of the triathlon. As a last resort, they could cancel the swim leg entirely to hold the duathlon with just running and cycling.

A particularly wet Parisian summer has forced a series of disruptions for swimmers and other athletes. Training for the swim leg of the triathlon was scrapped for the second day in a row on Monday due to Seine pollution. A skateboarding event for men was also postpone after rain the park court was soaked while delays hit the tennis courts at Roland Garros.