COVID-19 cases within Beijing’s Winter Olympic Games bubble reached the second highest since arrivals began on Feb. 4, with 45 new cases discovered, but organizers maintain the problem is under control and cases are restricted to the ‘closed loop.’

Games organizers said that while cases within the loop could continue rising, there was no reason for concern.

The loop allows athletes, officials and media to move between their accommodation and all Olympic venues, including the media center, but on official transport only.

However, they are forbidden to leave the bubble and move freely in the city, as China looks to minimize the risk of foreign visitors spreading the coronavirus during the Games.

“The numbers (of overall positive cases) have been different every day,” Huang Chun, the Games’ deputy director-general of the office of pandemic prevention and control, told a news conference on Saturday.

He said the different daily infection number from Games-related personnel, that had reached 55 on Feb. 2 and as few as two on Jan. 23, was related to the flight arrival times, with some tests conducted after midnight.

“The day before yesterday we had almost 20 flights, many flights arriving at midnight,” he said. “Some of the numbers have to be accumulated to the next day.”

Every participant has to arrive in Beijing with two negative PCR tests taken less than 96 hours prior to their departure.

They are then tested at Beijing airport before undergoing a rigorous daily testing routine for the duration of their stay in China.

“Even though the general number is increasing it is within our expectation,” Huang said. “We think the number will start to decrease.”

So far 2,877 athletes have landed in Beijing with about 2,900 expected in total. Other arrivals include team support staff as well as sports and competition officials and media.

A total of 353 Games participants have tested positive in Beijing since Jan. 23 both at the airport and in the loop.

Dozens of athletes have tested positive, with many still in isolation and the Games officially under way since Friday.

The latest cases involved two Swiss ice hockey players who went into isolation, according to the Swiss team on Saturday.

“In general we think the situation is under control. The cases within the closed loop have not spread and they do not affect the competition,” Huang said

In contrast to many countries seeking to live with COVID-19, China has isolated itself with a zero-tolerance policy, cancelling nearly all international flights.