PARIS, France (AFP)— Water tests in the Seine in Paris show the river is still too dirty to swim in, two months before the start of the Paris Olympics when it is set be used by athletes, data from a charity showed Wednesday.

French authorities have been in a race against time to clean up the Seine, which is set to host the swimming leg of the triathlon at the end of July as well as the open-water swimming in August.

Water charity Surfrider has been conducting regular tests to measure levels of two crucial bacteria which indicate the presence of faecal matter.

Its latest results showed levels of E. Coli and enterococci higher than authorised levels set by sports federations and European bathing standards.

One reading for E.Coli at the Alexandre III bridge was more than three times higher than the maximum level authorised by the triathlon and open-water swimming federations.

Heavy rainfall in May is likely to have contributed to what Surfrider called the “poor” water quality.

It noted that there had been heavy rain 36 hours before the tests, but only light rain in the 12 hours previous.

Heavy rainfall is known to overwhelm Paris’ more than century-old sewage system, leading to direct discharges into the river of untreated effluent.

Organisers are praying for fine weather during the July 26-August 11 Olympics and have been open about the possibility of needing to delay or even cancel the Seine swimming in the event of storms.

Although a new water treatment plant was inaugurated upstream of Paris at the end of April in Champigny-sur-Marne, another major Olympics-related water infrastructure project has yet to enter service.

A giant new underground storm water facility close to the Austerlitz train station in eastern Paris — which will stock water to prevent discharges into the river — is scheduled to come on stream in early June.

Cleaning up the Seine had been “probably the most difficult (Olympic) project to organise,” deputy Paris mayor Emmanuel Gregoire told reporters in April.

Around 1.4 billion euros ($1.5 billion) has been spent by French authorities upgrading sewage treatment and storm water facilities around Paris to reduce the amount of untreated faecal matter flowing into the river and its main tributary, the Marne.

The cleaning-up of the Seine has been promoted as one the key legacy achievements of the Paris 2024 Games, with mayor Anne Hidalgo intending to create three public bathing areas in the river next year.

She and President Emmanuel Macron have also promised to take a dip before the Games to demonstrate it is safe, with Hidalgo pencilling in June 23 for her swim, according to sources.

Olympic open-water swimming has been hit by pollution concerns in the past, notably in Rio in 2016 and Tokyo in 2021.