​Imports of canola into China will undergo more thorough inspections, the country's customs agency said Thursday, a move that comes after one Canadian company saw its permit to ship the crop to the country revoked.

Relations between Canada and China have been tense since December, when Canada arrested Chinese tech executive Meng Wanzhou in Vancouver at the request of the U.S. China warned of "grave consequences" if Canada did not immediately release Meng, the chief financial officer of Huawei.

U.S. prosecutors have filed charges accusing Meng, who is the daughter of Huawei's founder, of lying to banks about dealings with Iran. Huawei denies any wrongdoing.

Apparent targets of China's ire have included two Canadians detained on suspicion of harming national security, a third Canadian sentenced to death, and now Canada's eponymous oil product — canola.

While rapeseed is grown in many countries, the variant known as canola is most associated with Canada. The "can" in its name comes from the word Canada, named for the variety of rapeseed created by Canadian researchers that results in a bright yellow flower and a harvest that can be used as animal feed or crushed to create a vegetable oil for eating and cooking.

The Canola Council of Canada calls canola "Canada's greatest agricultural success story" and the world's only "Made in Canada" crop.

China's customs administration said in a statement posted to its website Thursday that four customs offices in China found pathogens including Leptosphaeria maculans, Pseudomonas syringae pv., Maculicola, Avena ludoviciana Durien,

Xanthium sp., and Amaranthus palmeri S. Watson in imported canola.

It confirmed that it revoked the export permit held by Richardson International Ltd., one of Canada's largest grain processors.

The statement seems to suggest other canola shippers may soon join Richardson in having their permits revoked.

The agency said stronger inspections and lab testing while canola imports are in quarantine were needed.

Canadian Agriculture Minister Marie-Claude Bibeau said in a statement Wednesday that the Canadian Food Inspection Agency conducted investigations after China issued notices of non-compliance on canola seed imports, including nine since January. She said the agency had not identified any pests or bacteria of concern.

"We want to know what the proof is that there is anything wrong with this canola," Canada's Minister of International Trade Diversification, Jim Carr, told CBC News on Wednesday. "We will ask officials to show the evidence once the evidence has been found."

China buys about 40 per cent of Canada's canola exports — roughly $3.6 billion worth last year — and the revocation of Richardson's permit hurts the entire chain of industries involved in the market, the Canola Council of Canada said.

"We think that there are no scientific reasons for this action," Foreign Affairs Minister Chrystia Freeland said Wednesday, "and we have already begun work on this issue."

The price of the crop has plunged on the heels of the uncertainty of the world's biggest importer potentially closing its doors to much of the supply.

The price of the active canola contract has fallen to $455 a tonne this week, it's lowest level since 2016.

Meanwhile, the dispute centred on Huawei is simmering.

Huawei announced Thursday that it is challenging a U.S. law that labels it a security risk and would limit its access to the American market for telecom equipment.