Open water swimming at the World Championships in Singapore has been postponed again because of "water quality levels exceeding acceptable thresholds," the governing body World Aquatics said in a statement Tuesday.

World Aquatics and organizers said that while water quality results have improved, the women's and men's 10-kilometer events scheduled for Wednesday morning have now been pushed back to the afternoon.

The women's 10-kilometre event, which was to have opened the program Tuesday, had already been postponed to Wednesday to be held the same day as the men's 10-kilometre event.

World Aquatics said both events will only take place if "acceptable test results" are returned Wednesday morning from samples collected on Tuesday afternoon.

Other open water events are scheduled for Friday, Saturday and Sunday.

Open water swimming was an issue in last year's Olympics in Paris with concerns about water quality in the Seine River. It was also an issue at the Tokyo Olympics in 2021 and the 2016 Olympics in Rio de Janeiro.

Water polo competition at the worlds is underway at an indoor venue.

The main even of the championships is eight days of swimming competition in the pool, which opens on July 27.