China has cancelled major Canadian agribusiness Richardson International Ltd's registration to ship canola to China, according to a document listing approved exporters posted on the website of the Chinese customs administration on March 1.

The document, a revised version of a notice first posted on Jan. 14, includes a note beside the entry for Richardson International saying, "Canola export registration already cancelled".

It wasn't immediately clear why Richardson's exports into China, the world's top importer of canola, had been halted. Officials at China's General Administration of Customs didn't immediately respond to requests for comment.

The move comes amid heightened tensions between the two countries in a dispute over trade and telecoms technology that has ensnared the chief financial officer of China's biggest smartphone maker, Huawei Technologies Ltd, who faces U.S. criminal charges.

Spokespeople at Richardson's headquarters in Canada couldn't be reached outside normal business hours.

Canada's embassy in Beijing referred Reuters' request for comment to government officials in Ottawa.

A Canadian grain industry source with knowledge of the matter confirmed Richardson's exports of canola to China had been halted. The person declined to be identified citing the sensitivity of the matter.