The 2024 Paris Olympic Games have been rocked by the forced postponement of the men's Triathlon just hours before it was due to begin.

The swimming leg of the event was due to be held in the River Seine, which has been banned for swimming for the last hundred years.

Despite that, French authorities have spent billions in attempting to clean up the river in a bid for both the triathlon and marathon swimming to be held on the river after the Opening Ceremony was held there on Friday.

Heavy rainfall recently has hampered efforts though, and tests revealed the river wasn't up to scratch to host the men's triathlon, which was supposed to get underway at 4pm (AEST) on Tuesday afternoon.

Instead, the men's event has now been pushed back to 6:45pm (AEST) on Wednesday, directly after the women's event which is still set to get underway as scheduled at 4pm (AEST).

It comes after training sessions were cancelled for triathletes in the river earlier this week while they have been on site, with tests conducted twice per day revealing consistently poor results of cleanliness.

The 3pm test carried out yesterday however - results for which were returned overnight in France - found contamination too high for the race to proceed.

There is an outside chance that if the river does not improve by the weekend, the postponed event could run without the swimming leg.

There is no back-up plan publically available for the marathon swimming to take place in Paris.