The World Triathlon Championship Series took a strange turn last weekend in Sunderland, with at least 57 people reporting diarrhea and other symptoms, according to reports.

The BBC reported that water testing from July 26 showed high levels of E. coli, while adding that approximately 2,000 people participated in swimming, running and cycling events that weekend in addition to the sixth race in the World Triathlon Championship Series schedule. 

The July 26 testing for E. coli occurred “outside of the Roker Pier arms and not in the body of water used for the swim,” the British Triathlon organization wrote in a statement, but previous and additional testing from July 25 and July 30, respectively, both met the standards to host the event.

One of those athletes, Jake Birtwhistle, revealed in an Instagram post that “he’d been feeling pretty rubbish since the race, but I guess that’s what you get when you swim in s–t.” 

“Some positives to take away leading into Paris in 2 weeks, but the swim should have been cancelled,” Birtwhistle, an Australian athlete who sits 35th the World Triathlon Series rankings, added in the caption.

The swimming portion of the event took place at Roker Beach, and The Guardian reported that the E. coli testing results weren’t known ahead of the event — though the cause of the vomiting and diarrhea is still being investigated.

“The team will undertake an investigation of cases as is routine when they are notified of gastroenteritis,” the UK Health Security Agency told the British Broadcasting Corporation in a statement. “This will involve a detailed questionnaire to establish more information on where illness may have been acquired. The team will also send sample pots to cases so that stool samples can be laboratory tested to discover the cause of illness and determine if there are any common pathogens involved. 

“This process is currently under way. As is standard in these investigations we would not speculate as to causes until we have received lab-confirmed cases and undertaken further epidemiological investigations.”

The final races in the 2023 World Triathlon Championship Series will be held in Pontevedra, Spain, from Sept. 23-24, with the previous five races occurring in Abu Dhabi, Yokohama, Cagliari and Hamburg.

Pierre Le Corre, a French athlete, won the Sunderland event.