China has suspended the license of a second major Canadian canola exporter, a blow to $2 billion worth of exports that is widely seen as retaliation for Canada's arrest of a top executive of Chinese tech giant Huawei. China's General Administration of Customs announced Tuesday on its website that officials have detected several hazardous organisms in shipments of canola seeds from Viterra Inc. It said shipments from the company have been blocked to prevent the introduction of pests to China.

China announced earlier this month it had halted imports from Canada's other major canola exporter, Richardson International Ltd, also citing contamination. Canadian Prime Minister Justin Trudeau said he might send a high- level delegation to China over the canola issue and acknowledged "challenges" in Canada's relationship with Beijing.

China was infuriated by the Dec. 1 arrest of Huawei's chief financial officer on a US extradition warrant alleging fraud and has since arrested several Canadian citizens on charges the government here says are spurious. "Clearly, they want to keep punishing us," said Guy Saint-Jacques, a former Canadian ambassador to China.

Canada last year exported $2.1 billion worth of canola seeds to China, by far its largest customer for the grain, which represented 17 percent of all Canadian exports to China. A spokesman for Viterra confirmed the ban and said all of its exports are tested to ensure they meet import standards. "Market access issues such as this one hurt our industry and Canadian farmers. We are hopeful for a quick resolution to this matter," the spokesman said in a statement.

Industry officials were skeptical about China's reason for halting imports. Richardson has denied China's allegations of pests. "We're very perplexed about how there can be any change in our canola between this week and eight weeks ago," said Brian Innes, spokesman for the Canola Council.

The arrest of Meng Wanzhou, the daughter of Huawei's founder at Vancouver's airport has led to the worst relations between Canada and China since the Tiananmen Square massacre in 1989. "We are in a real mess because of the extradition request of the Americans," Saint-Jacques said. "This is now translating to billions of dollars in lost sales. It's important for the U.S. government to be more forceful and try to help us out."

On December 10, China arrested two Canadians in an apparent attempt to pressure Canada to release Meng. A Chinese court also sentenced a Canadian to death in a sudden retrial in December, overturning a 15-year prison term handed down earlier. It is not the first time that Beijing has struck back against a nation that appeared to cross it.

In 2010, China suspended a bilateral trade deal with Norway and restricted imports of Norwegian salmon after the Nobel Peace Prize was awarded to Chinese political prisoner Liu Xiaobo. Britain and other countries were also retaliated against over official meetings with the Dalai Lama, the Tibetan spiritual leader who is considered a dangerous separatist by Beijing.