In this Aug 7, 2018 file photo, shrimp are displayed for sale inside a Vanguard hypermarket, operated by China Resources Enterprise Ltd., in Shanghai, China, on Aug 7, 2018. (QILAI SHEN / BLOOMBERG)

More samples of frozen shrimp imported from Ecuador have tested positive for the novel coronavirus this week as local authorities are stepping up precautions against the potential risk posed by the virus traveling through frozen food.

On Thursday, the Health Commission of Yunnan province said three of the 2,750 samples related to frozen shrimp shipments from Ecuador tested positive for the virus

The Ecuadorian government has held at least four rounds of talks with the Chinese government regarding traces of the virus found in its shipments to China and has promised to implement necessary measures to ensure the safety of exported products, the embassy of Ecuador in China said on its Weibo account on Wednesday.

On Thursday, the Health Commission of Yunnan province said three of the 2,750 samples related to frozen shrimp shipments from Ecuador tested positive for the virus. Tests on frozen shrimp and people who came in contact with them were negative.

On Wednesday, the virus control leading group in Chongqing municipality's Shapingba district said it detected the virus in the outer packaging of Ecuadorian frozen shrimp in a warehouse. The number of samples that tested positive were not specified.

The new findings were revealed as local governments nationwide are intensifying screening and testing of frozen products due to detection of the virus by customs officials in Dalian, Liaoning province, and Xiamen, Fujian province, earlier this month.

The General Administration of Customs said on July 10 that six samples recently taken from the interior of containers and outer packaging of frozen shrimp from Ecuador tested positive for the virus on July 3.

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Imports from the three Ecuadorian plants involved were immediately suspended, and all of their products were returned or destroyed, it said.

According to a statement posted by the embassy of Ecuador in China on its Weibo account, Ecuadorian Foreign Minister Luis Gallegos said several meetings had been held between Ecuador and China, including one between the director of China's top customs authority and the Ecuadorian minister for production, foreign trade, investment and fisheries on Tuesday.

There is currently no sufficient evidence to support the transmission of the virus through food, and no confirmed cases worldwide have proved to be infected by eating, experts have said

He said Ecuador has been actively seeking solutions to problematic shipments to China and promised to "perform necessary procedures" to guarantee the safety of its exports to the international market.

Gallegos added that Ecuador is not the only country facing trade restrictions imposed by China out of virus concerns and will continue to develop friendly and cooperative relations.

Speculations on the ability of the virus to spread through frozen food flared up in China when the recent outbreak in Beijing was reportedly tied to frozen products sold at a major wholesale market. The source of the outbreak is still under investigation.

There is currently no sufficient evidence to support the transmission of the virus through food, and no confirmed cases worldwide have proved to be infected by eating, experts have said.

However, cold food products, including seafood, and their packaging are likely to be contaminated and become a vector for the virus, and then spread to humans, Li Fengqin, head of the microbiology laboratory at the China National Center for Food Safety Risk Assessment, said in late June.

Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention, said the virus can survive for several months in cool or freezing temperatures.

By latching onto the surface of frozen foods or their packages, the virus can live up to two to three months, he said.

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During an interview with China Central Television last week, Wu said the presence of the virus in recent imports from overseas points to the likelihood that the virus can be brought in through seafood products, but more research is needed to determine if such a risk can trigger new outbreaks.