"I followed all the health rules as best as I could. Physically, I feel good but emotionally this is a dark day for me."
Dutch rower Finn Florijn was shattered after testing positive for COVID-19 after competing in the men's single sculls on Friday.
The 21-year-old had finished in fourth in his heat and was to have contested a repechage race on Saturday.
His case comes after a staff member of the Dutch rowing team, as well as two other Dutch athletes - taekwondo competitor Reshmie Oogink and skateboarder Candy Jacobs - also tested positive for COVID-19 earlier in the week.
Swimming great Pieter van den Hoogenband, chef de mission of the Dutch Olympic delegation, said they were doing everything to avoid positive COVID-19 tests.
'Stop the Olympics': hundreds protest outside opening ceremony
"Unfortunately, a new infection. It's obvious that we don't have any words for this," Mr Van den Hoogenband said .
"A young athlete who was making his Olympic debut here and has to put an end to it immediately."
Meanwhile, 29-year-old Portuguese surfer Frederico Morais issued a statement on social media, saying: "This is likely the saddest video I've ever had to post.
"In 2019, I qualified for the 2020 Tokyo Olympics that were postponed because of COVID-19. And now, because of the virus I won't be able to compete nor represent my country."
The Portuguese Olympic team said Morais, considered to be the best European surfer at the Games, would not travel to Tokyo as planned.
"I was very careful. I have been fully vaccinated for over a month, but ended up contracting the virus," Morais said in a statement issued through Portugal's Olympic team.
"I feel fine and I will carry out my isolation. I will be following every second of our team."