Chinese state media report parcels mailed from overseas may have spread the Omicron variant of the coronavirus in Beijing and elsewhere.
Globally, health experts have stressed the virus mainly spreads through respiratory droplets when infected people breathe, speak, cough and sneeze.
However, China has repeatedly emphasised the danger of infection from packaging, despite only trace amounts of the virus being found on such items, and it has boosted testing of items shipped from overseas.
The Communist Party newspaper Global Times cited the Beijing Center for Disease Control and virologists as making the link between the latest infections and packages from abroad.
Cases detected
The report on Tuesday said investigators found people newly infected had picked up packages mailed from Canada and the U.S..
China has locked down parts of Haidian district following the detection of three cases, just weeks before the Chinese capital is due to host the Winter Olympics. Another person in the southern technology hub of Shenzhen who tested positive for Omicron had handled packages sent from North America.