China's customs agency has stepped up efforts to prevent the novel coronavirus from being imported via cold-chain food with actions including broader communication with authorities in more than 100 countries, following a recent increase in cases of the virus entering the country on imported cold-chain food.

The General Administration of Customs said it has been in touch with authorities in all 109 countries that export cold-chain food to China and has demanded they urge food exporters to strictly follow sanitation guidelines and prevent coronavirus contamination of food and packaging bound for China.

The administration said it has also suspended imports of goods from all enterprises that have reported cluster infections among their employees. By Wednesday, 99 such companies from 20 countries had suspended exports to China, it said.

The administration has also intensified risk-monitoring of imported cold-chain food and increased sampling tests of higher-risk foods such as seafood. Intensified efforts will continue, including extensive sterilization of imported cold-chain food, to minimize risks of outbreaks of COVID-19 due to importation of the virus, the administration said.

Detection of the novel coronavirus, which causes COVID-19, on imported cold-chain food or its packaging has been reported in more places across China recently, prompting authorities to issue alerts about the need to handle such food properly to minimize the chances of infection. While the epidemic has been brought well under control domestically, importation of the virus poses a major risk.

In Xi'an, capital of Shaanxi province, two cold-storage facilities were sealed on Sunday after a package of pork imported from Argentina tested positive for the novel coronavirus. Eighteen people linked with the case have been put under quarantine for medical observation and have all tested negative for the virus, city authorities said.

Novel coronavirus has also been detected on imported cold-chain food or its packaging in some other places in the past few days, including Jinan, Shandong province, Wuhan, Hubei province, and Quanzhou, Fujian province.

Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention, said in a report by China Central Television on Sunday that a major reason that contaminated imported cold-chain food is being detected in more places across China is the worsening pandemic overseas, which has increased the chances of importing cold-chain food contaminated with the virus.

Another reason is falling temperatures in the northern hemisphere that have helped the virus survive longer. Meanwhile, local authorities across China have intensified monitoring of cold-chain food, resulting in timely identification of contaminated goods, he said.

Contaminated imported cold-chain food was suspected to be the cause of a COVID-19 outbreak in Beijing in June, as the virus was detected on cutting boards in a local wholesale market that had been used to process imported salmon. No locally transmitted COVID-19 cases had been reported in the city for nearly two months before the outbreak.

In October, researchers from the China CDC isolated live novel coronavirus for the first time from a package containing imported cod while tracing a COVID-19 outbreak in Qingdao, Shandong province. The discovery confirmed that contact with packaging contaminated with the novel coronavirus can cause infection.