The Tokyo Olympics has registered its first Covid-19 case in the athletes' village, organisers said on Saturday.
The development has added to concerns about infections at the Games that are scheduled to begin in six days.
"There was one person in the Village. That was the very first case in the Village that was reported during the screening test," Masa Takaya, spokesman for the Tokyo organising committee, said.
The person, whom organisers refused to identify, has been removed from the Village where thousands of athletes and officials will reside during the Games.
"Right now this person is confined to a hotel," Takaya said.
Seiko Hashimoto, the chief organiser of the Tokyo 2020 Games, said: "We are doing everything to prevent any Covid outbreaks. If we end up with an outbreak we will make sure we have a plan in place to respond."
The Tokyo 2020 Olympics, postponed for a year due to the global pandemic, is being held mostly without spectators and under tight quarantine rules.
Athletes are just starting to arrive for the Games, which will run from 23 July through 8 August.
Japan's public has been lukewarm about the Games amid a resurgence in new coronavirus infections and worries that an influx of foreign visitors may help turn the Tokyo Olympics into a super-spreader event, which in turn could put further strain on Japan's already stretched medical system.