The pollution levels in the River Seine have been found to be 'alarming' by a French water charity, just over a hundred days before it is to play host to a number of Olympic swimming events at the Paris Games.
As well as hosting a portion of the Opening Ceremony, the river that flows through the centre of the French capital is set to stage the marathon swimming events and the triathalon.
But the suitability of the venue has been called into question by the Surfrider Foundation, who have taken 14 samples from the Seine over the past six months and found the water to be potentially dangerous in all but one of their tests.
Sharing an open letter with its stakeholders, the charity stressed that they had 'rising concerns about the quality of the Seine' as well as 'the risks faced by athletes moving in contaminated water'.
Surfrider carried out their tests at the laboratory Eau de Paris alongside the environmental analysis group Analyco-Co between September 2023 and March, and concentrated on the area where the sports are set to take place - underneath the two bridges Alexandre III and Pont l'Alma.
A French water charity has found 'alarming' levels of bacteria in all but one of 14 samples taken from the Seine over the last six months
After suffering one of the wettest winters in 30 years, there are concerns over the impact of the city's sewage infrastructure (flooding from last weekend pictured)
President Emmanuel Macron is confident that the events will go ahead and has vowed to swim in the water
The measurements of E. coli and enterococci - bacteria which indicate the presence of faecal matter and which can cause serious illnesses - were found to be double and at times triple the maximum permitted amounts.
French authorities have been working hard to ensure that making the Seine swimmable is one of the lasting legacies of this summer's Olympic Games, with swimming in the river having been banned since 1923.
Over £1.2billion (€1.4bn) has been spent on upgrading the capital's sewage and storm water treatment facilities in the region over the last decade, with a major new storm water facility set to be inaugurated in April.
The city's sewage system can become overwhelmed by heavy rainfall, which can lead to untreated effluent flowing into the river - and those keen to push back against Surfrider's findings have stressed that the samples were taken amid one of the wettest winters in 30 years.
Parisian state official Marc Guillaume said that Surfrider had 'very poor knowledge of this issue' and added: 'There's no point doing tests today in the Seine and comparing them with what will happen next summer'.
'There has never been a question of opening the Seine for swimming all year round,' Guillaume continued.
Last August saw two test events staged in the river - but a slew of others cancelled after tests
Surfrider found up to triple the permitted amount of concerning bacteria present in some samples (testing in August 2023 pictured)
Such is the French government's confidence in the project that Paris mayor Anne Hidalgo and President Emmanuel Macron have pledged to swim in the river ahead of the opening of the games.
But should issues with pollution levels in the water persist, the events could be thrown in jeopardy, with no Plan B organised even in the event of bad weather.
'We will remain in this extraordinary location, no matter what happens,' said Tony Estanguet, head of the Paris 2024 organising committee, himself a former canoe champion. 'We want to preserve this ambition.'
Olympic organisers have only received permission to delay events by a few days should these issues arise.
Last summer planned women's and men's triathalons staged in the river went ahead to test the waters, but the para triathlon events and mixed relay races were called off after high levels of E. coli bacteria were detected.
Weeks earlier in July 2023, the 2023 World Aquatics Open Water Swimming World Cup had been cancelled due to high pollution levels.
The blame was levelled at heavy rainfall and a faulty sewer valve which led to the water becoming contaminated.
President of Paris 2024 Tony Estanguet said the events would 'remain in this extraordinary location no matter what'
Last month saw the Boat Race held in the River Thames where high levels of E.coli were found
Last month saw the annual Boat Race in the River Thames marred by contaminated water, with Oxford captain Lenny Jenkins citing E. coli in the water as one of the factors in their defeat at the hands of Cambridge.
Competitors had been warned in advance by organisers to cover any cuts and 'take care not to swallow river water' after tests around the Hammersmith Bridge stretch of the race indicated an average of 2,869 E. coli colony forming units (CFU) per 100ml of water.
To meet the Environment Agency's inland bathing water quality standards, the level should be below 1,000 CFU per 100ml.
River Action said the highest level it recorded was 9,801 CFU per 100ml, meaning it was nearly 10 times higher than levels found in bathing waters graded as 'poor' by Environment Agency standards.