The athlete training session for the Olympic marathon swimming was cancelled on Tuesday as concerns over the water quality of the River Seine continued at Paris 2024.

Athletes had been due to take to the water for familiarisation sessions ahead of the women’s 10 kilometre marathon on Thursday and the men’s race on Friday, but water quality assessments found that levels of Enterococci – an indicator of faecal pollution – were too high in the river.

A statement from World Aquatics said: “The water quality review showed E. coli levels ranged from 326 to 517 (considered “very good” to “good”) at the four collection points taken on 5 August between 5:00 and 6:00 a.m.

“However, Enterococci levels exceeded World Aquatics maximum thresholds during the morning review. The latest Enterococci samples (taken between 12:30 and 13:20 on 4 August) showed levels exceeding the maximum acceptable World Aquatics thresholds.”

Another familiarisation session is scheduled for Wednesday morning.

The statement added: “With a favourable weather forecast and forward-looking analysis, World Aquatics and Paris 2024 remain confident that the Marathon Swimming competitions on 8 and 9 August will proceed as planned.”

The tests on August 4 cited by World Aquatics were taken before the Seine was used for Monday’s mixed relay triathlon, but at Tuesday’s IOC briefing, Paris 2024 executive director of communications Anne Descamps said the relevant test had been taken in a part of the river not used for the triathlon.

Descamps added that the decision to cancel Tuesday’s session was “taken with an abundance of caution” as there is another session scheduled on Wednesday.

“We have to have familiarisation but there’s another familiarisation event which is planned tomorrow and for Paris 2024, we’re pretty confident in our ability to see what is happening in the weather forecasts will allow us to carry this out in good conditions,” Descamps said.

The issue of water quality had dominated the build-up to all three triathlons in the first week of the Games, with several familiarisation sessions cancelled and the men’s race delayed by one day to allow conditions to improve.

Monday’s mixed relay went ahead without the Belgian team, who withdrew after athlete Claire Michel fell ill having competed in the women’s race, finishing 38th, the previous Wednesday.

In the build-up to the Olympics, Paris invested 1.4billion euros trying to clean up the Seine, but water quality levels have dipped during the Games after a number of storms.