Some of China’s trade partners are pushing back against Chinese claims to have found samples of coronavirus in food or its packaging, saying that it has become an excuse to restrict trade.

China has rejected imports of pork, fish, beef and other products after purporting to find the coronavirus on or in packages of frozen food. In a recent meeting of the World Trade Organization, Canada, backed by five other nations including the United States, called the Chinese claims “unjustified trade restrictions.”

Critics say that Chinese authorities have never provided evidence of their claims of finding coronavirus, and that these claims are contrary to general scientific understanding of how the coronavirus survives.

The Chinese say that the restrictions are warranted because China, has virtually wiped out internal transmission of COVID-19 and must now be vigilant against reintroduction of the virus.