Concerns about the water quality in the Seine River led officials to call off the swimming portion of an Olympic triathlon training session for a second straight day Monday.

Organizers overseeing the event at the Paris Games are optimistic that triathletes will be able to swim in the city’s famed waterway when the competition starts Tuesday.

The sport’s governing body, World Triathlon, its medical team and city officials are banking on sunny weather and higher temperatures to bring levels of E. coli and other bacteria below the necessary limits to stage the swim portion of the race, which also includes biking and running.