Authorities in southern China said on Thursday that they had found traces of the coronavirus on frozen chicken wings imported from Brazil.

The surface of a sample of the imported chicken wings tested positive for the virus, the city of Shenzhen said in a statement on WeChat.

The city’s Epidemic Prevention and Control Office organised nucleic acid testing for everyone who may have been exposed to the products, authorities said, adding that the results came back negative.

In addition, China started screening all meat and seafood containers coming into major ports.

Screening efforts intensified after a coronavirus outbreak in Beijing in June was linked to the city’s Xinfadi wholesale food market.