China’s top prosecutor said he was certain two Canadian citizens detained in the country violated local laws and regulations and that both men remain under investigation.

“There is no doubt that the two Canadian citizens have violated China’s laws and regulations,” Zhang Jun, head of the Supreme People’s Procuratorate, said Thursday during a briefing in Beijing. “The investigation is in line with the due process of law, and we believe it will proceed accordingly.”

China has said that Michael Kovrig and Michael Spavor are being held on grounds of threatening national security. The Canadians have been detained for more than three weeks without a hearing.

China’s foreign ministry said last month that Kovrig and Spavor were “suspected of engaging in activities endangering national security,” without elaborating.

Kovrig, who is based in Hong Kong while on leave to work with the International Crisis Group, and Spavor, an entrepreneur who helped organize tourist trips to North Korea, were seized separately last month by China’s spy agency. The cases came nine days after Canada arrested Huawei Chief Financial Officer Meng Wanzhou Dec. 1 at the U.S.’s request.

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Neither China nor Canada have directly linked the two men’s cases, but they led to speculation of retaliation for Meng’s arrest. Canadian Prime Minister Justin Trudeau last month called the detentions “not acceptable” and said they were an example of worrying fallout from the unprecedented trade war between the U.S. and China

International Crisis Group Chief Executive Officer Robert Malley told Bloomberg News last month that Kovrig wasn’t a spy. “It’s pretty clear that what he was doing was neither secretive, nor in anyway endangering Chinese national security,” Malley said.

Little has been heard of the two men since they were taken. Kovrig has been held at a secret detention facility, questioned three times a day and unable to turn off the light, Bloomberg News reported. He was allowed a brief visit by Canadian Ambassador John McCallum in Beijing. McCallum has also met at least once with Spavor.

On Dec. 24, Foreign Ministry spokeswoman Hua Chunying dismissed criticism from the U.S. and Canada on its treatment of the two men, saying that China has abided by the law, protected Kovrig’s interests and fulfilled its consular obligations. She repeated that Canada should withdraw its arrest warrant on Meng.