PARIS (AP) — A test run meant to allow Olympic athletes to familiarize themselves with the marathon swimming course in the Seine River was canceled Tuesday over concerns about water quality in the Paris waterway.

World Aquatics made the decision to cancel the exercise at an early morning meeting, spokesperson Torin Koos said. Fluctuating bacteria levels in the long-polluted waterway have been a constant concern throughout the Games with the swimming portion of the triathlon and the marathon swimming events both scheduled to be held in the river.

Another marathon swimming test event is scheduled for Wednesday, and organizers will decide early that morning whether it will go forward, Koos said. The women's marathon swim is set for Thursday, while the men are scheduled to race Friday.

The cancellation of Tuesday's marathon swimming test event comes a day after the triathlon mixed relay event was held in the river that runs through the center of the French capital. World Triathlon released data Tuesday showing that when the triathletes swam Monday, the levels of fecal bacteria E. coli and enterococci were within acceptable levels for the length of the triathlon relay course.

The swimming portion of the triathlon and the marathon swim both start and finish at the Pont Alexandre III, but the marathon swimming course extends farther down the river. The marathon swimmers do laps on the course for a total of 10 kilometers (6.2 miles.)