China’s restrictions on imports of frozen food, due to fears of the coronavirus being imported in food or on its packaging, are getting pushback from foreign suppliers who say it amounts to a restriction on trade.

Chinese authorities have insisted for months that there is a danger of the coronavirus arriving in shipments of frozen food. It has imposed elaborate testing protocols that have lengthened the time it takes to clear incoming shipments from a week to a month.

“They are taking each single box and spreading it out in a big room…and then they spray something on the outside of the box,” a seafood exporter told the Wall Street Journal.

Some smaller Chinese cities are refusing shipments of imported meat and other foods entirely, while supermarkets in Beijing and Shanghai are required to have separate display sections for imported meat.

China claims that these measures are necessary because it has largely controlled COVID transmission within the country and needs to be especially vigilant about keeping the virus out. Most outside authorities say there is no scientific basis for believing that the coronavirus can be transmitted via food shipments.

Critics charge that China is engaging in trade restrictions with coronavirus concerns as a cover, and trying to deflect attention away from the fact that the coronavirus originated there.