China is advising citizens to use face coverings and gloves when opening mail, particularly from foreign countries, after authorities speculated that the first case of the Omicron coronavirus strain discovered in Beijing may have arrived via a package from Canada.

Chinese social media users have backed Beijing's notion that Canada smuggled "poison" into the Chinese capital, thereby explaining how the Omicron variant of COVID-19 entered the city.

According to Insider, one viral post on Weibo stated that someone "deliberately" mailed the suspected tainted letter to Beijing, urging other users to "be cautious about foreign mail."

Authorities have committed to beef up disinfection of international mail and to require full vaccination of postal personnel handling it.

The precautions come less than three weeks before the capital's Winter Olympic Games opening ceremony and as numerous Chinese towns work to contain new coronavirus outbreaks.

"It is plausible to infer that this was purposely poisoned. Certainly, one must exercise caution when dealing with international mail," one Weibo user commented on a popular post about the incident that had over 50 million views at the time of writing.

"Reduce purchases of foreign items and letters from foreign countries," state broadcaster CCTV advised late Monday in a social media post.

Beijing had locked down an office building on Saturday after officials detected the Omicron variant's first arrival into the city, NextShark earlier reported.

The Chinese government has claimed the individual infected with the virus did not leave the city and had no contact with another confirmed case in the preceding 14 days.

Pang Xinghuo, deputy head of the Beijing Center for Disease Prevention and Control, believes the individual was infected via "a material from abroad," a 22-page letter from Toronto that arrived in Beijing on Jan. 11.

The charge came as China's view of Canada reached a new low. According to a survey conducted in 2021 by the state-run media outlet Global Times, Canada was China's least preferred country.

China used to send almost three-quarters of a million tourists to Canada each year, but animosity between the two countries have risen significantly since 2018, when their governments clashed over Canada's detention of Huawei's chief financial officer, Meng Wanzhou.

Meng was arrested and held by Canada on accusations of breaking U.S. trade restrictions.

China has been an outlier in saying that COVID-19 can be spread via cold-chain imports such as frozen meat and seafood, despite the World Health Organization's downplaying the risk.