The World Triathlon Para Cup in Paris had its swimming leg cancelled following “discrepancies” in water quality tests from the River Seine.
Saturday’s race was a test event for next year’s Paris Paralympics.
World Aquatics said the decision was made so “not to put the health and safety of the athletes at risk”.
Britain’s Dave Ellis and guide Luke Pollard won gold in the men’s PTVI class, while Claire Cashmore took silver in the women’s PTS5.
On Thursday and Friday, the elite men’s and women’s triathlon races included the swimming leg in the Seine, with Great Britain’s Alex Yee and Beth Potter each winning gold.
However, earlier this month, an Open Water Swimming World Cup event – another test event for Paris 2024 – was cancelled after water quality in the Seine was ruled to be “below acceptable standards.”
The Seine is scheduled to host marathon swimming, triathlon and Para-triathlon events at the Olympics and Paralympics.
“We have observed a significant discrepancy between the latest water quality tests provided by the laboratory and the high frequency sample analysers,” World Aquatics said in a statement on Saturday.
“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.”
Swimming is set to be one of the major legacies of the Games thanks to a 1.4bn euro (£1.2bn) regeneration project in Paris, with three open-air swimming areas accessible from the quayside by 2025.
