Yesterday saw triathletes compete in a 1,500 metres swim in the river as part of a trial run for next year’s Olympics in Paris.

But a decision has been made to pull the plug on the swimming section of today’s World Triathlon Para Cup over health fears.

Instead, World Triathlon has agreed to adopt a duathlon format with athletes set to compete in running and cycling segments across the six classes.

"At the daily meeting to review water quality earlier today at 3.30am [local time] with representatives from World Triathlon, including the three technical delegates and the medical delegate, Paris 2024, the City of Paris and the public authorities, we have observed a significant discrepancy on the data between the results of the latest water quality tests provided by the laboratory and the high frequency sample analysers," a statement from World Triathlon read.

"Considering this discrepancy, and not to put the health and safety of the athletes at risk, the decision has been made to cancel all the swim activities planned for today.

"The Para triathlon competition will be contested on a duathlon format, starting at the scheduled time.

"Paris 2024, the City of Paris and the public authorities are investigating the data discrepancy and will share more details as soon as more information is available."

Para triathletes are set to compete in a 2.5 kilometres run, followed by a 18.5km bike ride and a 5km run.

The Île-de-France said the decision to cancel the swimming events was a "precautionary measure" as it carries out an investigation into the discrepancy.

A further meeting is set to be held tomorrow morning to determine whether the Seine will be used for the World Triathlon Mixed Relay Series that day.

The decision not to use the river over health concerns is another blow to Paris 2024 organisers.

World Aquatics was forced to cancel its Open Water Swimming World Cup event, which was also a Paris 2024 test event, after the Seine's water quality was judged to be below acceptable standards.

French officials blamed the pollution on above-average rainfall in Paris, which had caused sewers to overflow.

They have also insisted that the "most significant" water quality improvement projects were due to be finished in the coming months in a bid to cope with "exceptional weather events".

Paris Mayor Anne Hidalgo has promised that the Olympics and Paralympics in the French capital will be the catalyst for a massive clean-up that would lead to three new sites being opened in 2025 so that public swimming would be allowed in the Seine.

Today’s ruling also comes after it was revealed that 57 athletes that participated at the World Triathlon Championship Series in Sunderland earlier this month had fallen sick after swimming at the Roker Pier.