Paris: With only weeks remaining for the commencement of swimming competition as part of the Paris Olympics, recent tests conducted revealed elevated levels of E. coli and other bacteria in the Seine River, raising serious concerns.

The contamination is attributed to heavy rainfall in Paris. As per the reports of monitoring group Eau de Paris, the level of contamination has exceeded safety limits for athletes.  

Marathon swimming races covering distances of 10 kilometres (6.2 miles) for both men and women are scheduled on August 8 and 9 respectively, in waters that were historically polluted before a $1.5 billion investment was made ahead of the Olympics.

"We are confident that we will swim in the Seine this summer," stated IOC official Christophe Dubi during an online briefing on Thursday, following updates from Paris city officials and Olympic organisers.

Despite the IOC's assurance, the ultimate decision regarding the safety of the events for athletes should be left to the governing bodies of individual sports, namely World Aquatics and World Triathlon.

Concerns about the Seine's water safety for the Olympics arose last August when some test events were cancelled due to unusually heavy rains.

According to European standards, the acceptable limit for E. coli is 900 colony-forming units per 100 millilitres, a benchmark also used by the World Triathlon Federation to assess water quality for competitions.

Recent tests conducted in the first eight days of June indicated that E. coli levels frequently exceeded these thresholds. However, levels of enterococci, another bacteria tested, mostly remained within safe limits. There was noted improvement in water quality from June 1 to June 9, primarily due to better weather conditions.

Rainwater containing faecal bacteria infiltrates the sewer system and is diverted into the Seine to prevent street flooding. In response, a large reservoir with a capacity of 50,000 cubic metres, designed to store excess water during heavy rainfall, was inaugurated in May.

The water quality of rivers in major cities can be influenced by various factors such as runoff, illegal chemical dumping, and boat traffic.

Earlier this week, Paris' mayor, Anne Hidalgo, reiterated her commitment to swim in the river before the competition begins. However, she announced on Tuesday that her swim has been postponed until after the snap elections in France, which conclude on July 7th. AP