For the third time in its history, Paris began the Olympic Games under water, despite the fact that the weather forecast predicted only sporadic showers. In this situation, it was expected that the rain would increase the bacteriological risk in the Seine due to the influx of waste into the river that crosses the French capital.

Although the Olympic organisers "trust" that the events scheduled for Tuesday and Wednesday will go ahead as planned, they had to announce the suspension of the training sessions early on Sunday morning after carrying out water quality tests on the Seine.

The organising committee of the Games, the International Triathlon Union and the local authorities "jointly decided to cancel the swimming leg of the familiarisation triathlon" scheduled for Sunday because "the water level did not provide sufficient guarantees", they said in a communiqué.

The river that runs through Paris was declared safe for swimming following tests carried out in mid-July, although doubts remained about its suitability for the competition. Despite a multi-million euro environmental clean-up effort, water quality remains largely dependent on natural factors and rainfall.

The organisers, who met to assess the water quality of the Seine, "reaffirmed that the priority is the health of the athletes", hence the suspension of this part of the triathlon training at 4am on Sunday following rigorous testing, as previously reported by Inside The Games.

The triathlon is the first Olympic event scheduled for the Seine, before the open water swimming events in the second week of the Games. If conditions improve, the men's and women's swimming events will take place on Tuesday and Wednesday respectively.

"Given the weather forecast for the next 48 hours, (the organisers) are confident that the water quality will be back below the limits before the start of the triathlon events on 30 July."

In the event of heavy rainfall, untreated sewage can flow into the river, increasing levels of E.Coli and Enterococcus, which pose a health risk on contact at elevated levels.

If the water quality shows high levels of contamination, an alternative would be to postpone the competition for a few days or move the triathlon swim to Vaires-sur-Marne, on the Marne River east of Paris, although no information has been provided about any changes or a Plan B.

The International Triathlon Union has set the limit for E. coli (a bacteria found in faeces) at 500 colony-forming units per 100 millilitres of water. A similar issue arises with the second bacteria measured by the International Triathlon Union, Enterococcus. The limit is 200 CFU/100 ml and, according to the organising committee, more than 1,400 units were detected at the Pont Alexandre III on 10 July and 800 units on 21 July.

The men's individual triathlon is scheduled for Tuesday 30 July and the women's for Wednesday 31 July, both at 20:00 local time, while the mixed relay is scheduled for Monday 5 August at the same time.

The same problem could affect the open water swimming events, with the women's 10km on Thursday 8 August and the men's 10km on Friday 9 August at 19:30.