Training in the river was halted last week, and the men’s individual race was postponed by 24 hours due to pollution issues. It was eventually held after the women’s event on Wednesday.

A heavy rainstorm on Thursday night is suspected to have worsened the river’s water quality, as downpours often lead to sewer overflows into the Seine.

Paris 2024 spokeswoman Anne Descamps informed reporters on Saturday evening that training had been canceled for Sunday. “It follows the rain that occurred in the last days,” she said. 

“We are expecting improvements regarding the weather forecast... we are hopeful that we can organise the competition tomorrow and we will take the decision as planned tomorrow morning.” She did not provide the latest water quality readings.

The mixed relay triathlon includes two men and two women per team competing in a sprint format: a 300-metre swim, a seven-kilometre (4.3-mile) bike ride, and a 1.8 kilometre run. It was first introduced at the Tokyo Olympics in 2021, where Britain secured gold. The Seine is also scheduled to host the marathon swimming events, a 10-kilometre race, on 8 August for women and 9 August for men.

Last week, many triathletes were caught off guard by the Seine’s strong currents, with some expressing concerns about the water quality and delays affecting their training and the men’s competition. 

“While swimming under the bridge, I felt things and saw things that you shouldn’t think about too much,” Belgian competitor Jolien Vermeylen told the Parisien newspaper.

Paris organisers stated that the water quality was "very good" based on the criteria used by World Triathlon. The levels of E. coli bacteria, a key indicator of fecal contamination, were recorded at 192-308 colony-forming units per 100 millitres (cfu/ml) on the race day, well below the upper limit of 1,000 cfu/ml.