Tokyo's Shinjuku Ward has seen sharp rises in the number of coronavirus tests and the percentage of those testing positive.
Health officials and workers are concerned that a further rise in infections could overwhelm the ward's testing capacity.
The organizer of a stage production in Tokyo says 37 people, including actors and members of the audience, have been confirmed to be infected with the coronavirus.
The play ran between June 30 and July 5 at Theater Moliere in Shinjuku Ward.
More people appear to be commuting to work in Tokyo, despite the Japanese government's extended state of emergency declaration over the coronavirus.
The government issued the declaration on April 7 for Tokyo and six other prefectures, and has since extended it nationwide. People are still being encouraged to stay indoors, work from home and stagger commuting hours.