The Olympics' triathlon swimming training session scheduled for Sunday has been cancelled after recent heavy rain in Paris affected pollution levels in the Seine, organisers said in a statement.
"The tests carried out in the Seine yesterday revealed water quality levels that in the view of the international federation, World Triathlon, did not provide sufficient guarantees to allow the event to be held," said Paris 2024.
"This is due to rain that has fallen on Paris on July 26-27."
Organisers said they were "confident" water quality would improve again before the triathlon events begin on Tuesday with the men's race.
The French capital has been working on cleaning up the Seine so people can swim in it again, as was the case during the 1900 Paris Olympics.