Health official Pang Jinghuo said international mail “cannot be ruled out” after a woman in Beijing contracted omicron.
Chinese officials fear that international mail may be to blame for the two Omicron cases reported on opposite sides of the country.
Beijing reported its first omicron case on Saturday, according to local media, in which a COVID-positive woman had no contact with other infected people.
Pang Jinghuo, deputy director of the city’s Centers for Disease Control and Prevention, told a news conference on Monday that mail from North America “cannot be ruled out” as a source of infection.
The Omicron case was mailed on January 11 from Toronto, Canada. The mail was in transit through the United States and Hong Kong.
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According to local media, Ms Pang said Omicron was detected on parts of the mail. Tensions are similar to those seen in North America and Singapore in December.
The second Omicron case was reported in Shenzhen on Sunday.
Local media reported that health officials believe the virus came in the case after coming into contact with infected goods from abroad.
Officials have now told residents to avoid placing orders from abroad to curb the spread of the virus ahead of the Winter Olympics in Beijing.
Postal workers have also been ordered to disinfect the packaging of international mail amid the latest Omicron scare.
China, the country where the coronavirus first emerged in late 2019, has attempted to maintain its COVID-zero strategy during the pandemic and ahead of the Games.