There were 55 new positive results for Covid-19 at the Winter Olympics on Wednesday, the highest daily total so far.
The figures were found among Olympic Games-related personnel in Beijing.
There were 26 positive cases in the closed loop system which separates Olympics personnel from the public, and 29 among new airport arrivals.
“The numbers are very small,” said Brian McCloskey, chair of the Beijing 2022 medical expert panel.
“We are confident that the system will work. But we are not relaxed. We keep all measures in place.”
Since 23 January there have been 287 positive cases among Games-related personnel from 610,000 tests.
Although live sport began on Wednesday with mixed doubles curling, the opening ceremony on Friday marks the official start of the 24th Winter Games.
Beijing 2022 is the second Olympics to take place during the Covid pandemic. As in Tokyo last summer, there will be no fans, friends or family present in the stands.
All participants, from athletes to volunteers to the media, must take daily PCR tests and are enclosed in a strict closed-loop system in which movement is limited.
Face masks are mandatory at all times, except for during competition and training, when eating and drinking, or alone in rooms.