The Tokyo Olympic organizing committee said the two athletes who tested positive for the coronavirus on Sunday and a staff member who was announced to have tested positive on Saturday belong to the same team.
The two were the first to test positive among athletes who are staying at the Athletes' Village.
The announcement was made during a news conference at the main press center on the measures being taken against virus infection and the effects of hot weather.
The committee said the three are being isolated in a hotel outside the village. Other members of the team are staying in their own rooms and taking their meals there.
The chief of the committee's main operation center, Nakamura Hidemasa, said it is most important to minimize risks and take swift action.
He said infection is under control, and that the operation center will create a safe Athletes' Village through testing and by quickly isolating those who test positive.