Organisers cleared the Olympic women's and men's triathlons to go ahead on Wednesday after the latest Seine river water tests showed lower levels of bacteria, ending days of uncertainty over whether the central Paris swim was viable after heavy rains.

The men's triathlon had been scheduled to take place on Tuesday but was postponed until Wednesday after the river failed water quality tests.

News that the races would go ahead on Wednesday came as a relief for teams and athletes, as well as for Paris authorities who have promised residents a swimmable Seine as a long-term legacy of the Games, with the triathlon a very public test.

"It is with great joy that we received this news," Benjamin Maze, technical director for France's triathlon federation, said. "Now that we know we will race, we can mentally switch fully into competition mode."

Fifty-five women representing 34 countries and regions will kick off the contest at 2pm Hong Kong time, with France's Cassandre Beaugrand and Britain's Beth Potter, two of the top contenders for gold, set to dive into the river side by side.

The SAR's Jason Ng will participate in the men's event, which begins at 4.45pm, immediately after the women's race.

"The results of the latest water analyses...have been assessed as compliant by World Triathlon allowing for the triathlon competitions to take place," Paris 2024 and World Triathlon said in a statement.

Paris has spent US$1.52 billion of public money on wastewater infrastructure to contain sewage and minimise spillage into the river, and Mayor Anne Hidalgo took a dip earlier this month in a bid to convince doubters that the water will not make them ill. (Reuters)