China is once again implying that “imported” COVID-19 cases may have been caused by imported foodstuffs. First it was shrimp and salmon from Norway and Ecuador, now it’s frozen chicken wings from Brazil.

Reuters reported that authorities in Shenzen found traces of the virus on the packaging of the chicken wings imported from Brazil, a country with one of the worst outbreaks in the world. One day later, a similar discovery was made in Xian City, though this time on packages of frozen shrimp from Ecuador.

Shenzhen’s health authorities did thorough testing and tracing, and eventually said they found no new cases connected to the packaging.

Reports of contaminated food have led supermarkets and markets across the country to ditch fresh salmon and shrimp, destroying millions of dollars of product. However, we’ve started to wonder whether the tests used by the Chinese authorities might be set off by something else in the packaging.

The Brazilian embassy in Beijing did not immediately respond to a request for comment.

“It is hard to say at which stage the frozen chicken got infected,” said a China-based official at a Brazilian meat exporter.

The Shenzhen Epidemic Prevention and Control Headquarters said the public needed to take precautions to reduce infection risks. Meanwhile, the WHO said Thursday that there are no confirmed examples of the virus being “food borne”.