A coronavirus cluster overshadows the run-up to the Games as a U.S. gymnast tests positive.

Such is the unease that Toyota, one of the prime corporate sponsors of the Games, announced Monday it would not run any Olympic-themed television advertisements during them.

“There are many issues with these Games that are proving difficult to be understood,” Jun Nagata, the company’s chief communications officer, told reporters, according to The Associated Press.

The three people who tested positive inside the Olympic Village were from the South African soccer team, including two athletes and one official. They were isolated in a separate building while an additional 21 people in close contact with them are quarantining in their rooms.

Masa Takaya, a spokesman for the Tokyo organizing committee, said athletes who were in close contact with those who tested positive would be allowed to train if they otherwise follow the isolation restrictions. Athletes are tested daily and if they test negative within six hours of a competition, they will be allowed to play.

Another six athletes and two Olympics staff members from Britain were also isolating after they had been informed that they had sat near a person on their flight to Tokyo who had tested positive for the coronavirus at the airport.

The Associated Press reported that Ondřej Perušič’, a beach volleyball player competing for the Czech Republic, had also tested positive in the Olympic Village.

At a news conference over the weekend, Christophe Dubi, the International Olympic Committee’s sports director, said “there is no such thing as zero risk,” adding that through testing and rigorous contact tracing and quick isolation, the Olympic Village would be “a Covid-safe environment but not Covid free.”

The Japanese public remains anxious about the staging of the Olympics amid a slow rollout of vaccines and a recent rise in coronavirus cases in the capital. Daily case counts have exceeded 1,000 for several days for the first time since mid-May. Tokyo is under a state of emergency. A poll by the Kyodo News, a wire service, released over the weekend showed 87 percent of those surveyed said they were worried about hosting the Olympics during the pandemic.