After months of speculation about whether the water in the Seine was clean enough for Olympic athletes to compete in, authorities have determined after last-minute testing that the river’s water is safe for swimming.

After tests of the Seine’s water quality came back positive on Wednesday morning Paris time, the men and women will swim in back-to-back races as part of a triathlon, starting at 8 a.m. local time. The men’s race was originally scheduled for Tuesday but was postponed after the Seine’s water failed tests.

“The latest water quality analysis results, received at 3:20 a.m., have been assessed by World Triathlon as meeting the standards and clearing the way for the triathlon to go ahead,” World Triathlon, the organisers and governing body of the Paris Games, said in a statement.

After the race, Team USA triathlete Taylor Spivey said he “swallowed a ton of water” during the triathlon swim in the Seine, a river that has historically been so polluted that swimming in it has been illegal for the past century.

Spivey, who finished 10th in the race, told NBC News that his biggest concern wasn’t the water quality, but the “exceptional” and “shocking” strength of the current, which he said was so strong that the race could have been canceled.

“The flow was incredible,” she said. “It felt like I was on a treadmill in one place.”

When asked about the quality of the water, she added, “I’ve been taking lots of probiotics for the past month. We’ll see how it goes.”

Cassandre Beaugrand of France won the gold medal ahead of Julie Delong of Switzerland, who took the silver medal, while Beth Potter of Great Britain took the bronze medal.

The Seine’s water quality has caused a bit of a stir in the run up to the events, as organizers rush to clean up the polluted waterway for prime-time attention. For months, France has been testing samples from the river for the presence of pathogens such as E. coli and enterococcus. High levels of E. coli put swimmers at risk of developing gastrointestinal illness.

The Seine has not passed these tests after wet weather, when storms can send runoff and sometimes sewage into the river.

Swimming in the Seine has been banned for more than a century because it was deemed too polluted, but the city of Paris led a $1.5 billion effort to clean up the river and strengthen waste-treatment systems ahead of the Olympics.

As the first event approached, organizers were hoping for sunny weather that would reduce overall pollution and allow ultraviolet light to inactivate some bacteria.

But the weather rarely cooperated.

last year, Test Event Triathlon rehearsals were canceled due to concerns about water quality after the rains.

The opening ceremony, which included a boat parade on the Seine, took place in pouring rain on Friday, which continued into Saturday.

Pollution from the rain forced organisers to cancel two days of swimming training on Sunday and Monday, then postpone the men’s triathlon originally scheduled for Tuesday morning.

“I’m just trying to focus on what I can control,” U.S. triathlete Kirsten Kasper told NBC News on Tuesday. “We swim in a lot of cities and water quality is often an issue, but I just have to trust that the race organizers are doing the testing and doing what it takes to make sure we’re safe.”

Water experts said the difficulty of keeping the Seine clean enough could draw attention to a broader problem of environmental pollution shared around the world.

“In large cities, it’s very difficult to control the amount of human waste that you see,” said Katie Graham, an assistant professor in the Georgia Institute of Technology’s College of Engineering. “The public assumes that a lot of these problems have been completely solved, but that’s by no means the case.”

NBC News is a unit of NBCUniversal, which owns U.S. media rights to the Olympics through 2032, including the 2024 Paris Games, which begin July 26.

Evan Bush reported from Seattle and Alexander Smith from Paris.