Traces of the coronavirus have been detected in two Chinese cities on food and packaging imported from South America, prompting wide-scale testing. In Xian, capital of northwest China’s Shaanxi province, a sample of packaging on frozen shrimp from Ecuador tested positive for the pathogen on Wednesday night, provincial authorities said on Thursday. Further tests were being carried on other products and people who had been in contact with them, they said. Meanwhile, authorities in Shenzhen, Guangdong province, said they had found the coronavirus on the surface of frozen chicken wings imported from Brazil. Other food products were being tested for the virus, they said. The sample was found positive for the virus during routine sample tests in Longgang district on Tuesday, and confirmed during a re-examination by the city and the Guangdong Centre for Disease Control and Prevention the next day, an official notice from the Shenzhen Municipal Health Commission said on Thursday morning. Does Covid-19 spread through food? The evidence says ‘highly unlikely’ All personnel who might have come in contact with the product were given nucleic tests, close contacts of the sample were being monitored and all stored products had been tested and all were found to be negative to the virus, the notice said. In addition, all sold products are being tracked, and packaging and storage areas of similar products are being sanitised. “Shenzhen will keep tracking and testing all relevant frozen foods. The government also would like to remind residents to be cautious when purchasing imported frozen meat and seafood, as well as apply personal protection,” the commission said. There have been sporadic incidents where the virus has been found on surfaces or packaging of imported foods. On Tuesday, authorities in the eastern Chinese port city of Yantai said the virus was detected on the packaging of imported frozen seafood . Last month, the virus was also detected on the packaging and in a container of imported frozen shrimps, but the food safety chief said the discovery did not mean the virus could be transmitted via food packaging. It has raised questions about the processing and hygiene standards of China’s wet markets . Authorities have conducted more coronavirus tests on imported food after a resurgence of Covid-19 cases in Beijing in mid-June linked to a food market where the coronavirus was found on a cutting board used for imported salmon . Experts have said the fish itself was unlikely to carry the virus. The National Health Commission also issued guidelines on Wednesday stressing the need for personal protection at seafood stalls across the country. Requirements include establishing hygiene and health monitoring in wet markets, sanitising standards in public areas and improving personal hygiene and emergency procedures. Virologists have also suggested that customers should clean ingredients before cooking and ensure foods are thoroughly cooked to kill the coronavirus and other pathogenic microorganisms.