Is the Seine safe for Olympians to swim in?

The Seine has been a central feature of the Paris 2024 Olympic Games, beginning with the memorable opening ceremony. Now, however, it's making headlines again, but for less celebratory reasons.

On Tuesday, an Olympic swimming test has been canceled after larger concerns over the Seine river's water quality. The test run is meant to grant Olympic swimmers the ability to learn the marathon swimming course but the exercise was canceled by World Aquatics, the international body recognized by the International Olympic Committee, The Associated Press reported. Fluctuating bacteria levels in the polluted Seine have "showed levels exceeding the maximum acceptable World Aquatics thresholds," according to World Aquatics.

This cancellation comes days after Belgian athlete Claire Michel fell "unfortunately ill" after swimming in the Paris waterway, prompting Belgium's Olympic committee announcing on Sunday that it would withdraw from the mixed relay triathlon, reports the AP.

Olympic organizers did not elaborate on Michel's illness. Swiss swimmer Adrien Briffod also withdrew due to a gastrointestinal infection, but Simon Westermann replaced him, reports CNN. It's unclear whether Briffod's infection was related to the Seine's water quality. The mixed relay triathlon proceeded as scheduled on Monday with World Triathlon released data showing that the Seine's levels of fecal bacteria E. coli and enterococci were within acceptable levels for the length of the relay course.

Another marathon swimming test is scheduled for Wednesday. The event's organizers will decide if it will go forward on Wednesday morning. As of this report, the marathon swimming competitions will proceed as planned on Aug. 8 and 9.