The men’s Olympic triathlon was postponed just hours before it was due to start on Tuesday following a 3.30am inspection of the Seine, which found that pollution levels were still too high for athletes to safely swim in.

In a statement, organisers said that the heavy rain over Paris on Friday and Saturday had compelled them to “reschedule the event for health reasons.”

With rain also forecast for later this week, the men’s race has been rescheduled for 10.45am on Wednesday following the conclusion of the women’s race, which is due to start at 8am.

However athletes included Team GB’s Alex Yee and Beth Potter, who are favourites for the men’s and women’s race, face an anxious wait to see if water quality improves.

There is also a risk of thunder and lightning in Wednesday’s forecast, which could throw yet another potential spanner in the works.

In a statement, organisers confirmed that the decision was taken following a 3.30am meeting and water quality test attended by Paris 2024, World Triathlon, the International Olympic Committee, Météo France, the City of Paris and the Prefecture of the Ile-de-France Region.

“Considering the latest weather information, it has been decided to schedule the men’s triathlon event on 31 July at 10h45,” the statement said, “The women’s triathlon is due to take place the same day at 8am.

“Both triathlons are subject to the forthcoming water tests complying with the established World Triathlon thresholds for swimming. The original contingency day also remains in place for August 2, for further considerations.

“Paris 2024 and World Triathlon reiterate that their priority is the health of the athletes. The tests carried out in the Seine today revealed water quality levels that did not provide sufficient guarantees to allow the event to be held.”

“Unfortunately, meteorological events beyond our control, such as the rain which fell over Paris on 26 and 27 July, can alter water quality and compel us to reschedule the event for health reasons. Despite the improvement on the water quality levels in the last hours, the readings at some points of the swim course are still above the acceptable limits.”

Swimming in the Seine has been banned for over a century. But since 2015, organisers have spent around £1bn to ensure a cleaner river for the Games – and to allow Parisians to swim in it afterwards.

Renovations have included the construction of a giant basin to capture excess rainwater and stop too much sewage from flowing into the river – as well as renovating infrastructure and upgrading wastewater treatment plants. However the heavy recent rain has pushed more sewage and E Coli into the Seine.

Organisers said they would provide more information regarding tickets and broadcast of the events on Wednesday July 31 in the next hours.