Foreign Minister Chrystia Freeland said Wednesday a second Canadian was being questioned by China, after Beijing earlier this week notified Ottawa it had detained a former Canadian diplomat.
"We are aware of a Canadian who got in touch with us because he was being asked questions by Chinese authorities," Foreign Minister Chrystia Freeland told a press conference.
Freeland offered few details, but added her ministry had not been able to make contact since the notification.
"We are working very hard to ascertain his whereabouts and we have also raised his case with Chinese authorities," she said.
It comes days after former Canadian diplomat Michael Kovrig was detained on a trip to Beijing.
Canadian officials said they were officially informed of Kovrig's detention via fax early on Monday.
"Canada is deeply concerned about the detention of Mr. Kovrig and Canada has raised the case directly with Chinese officials," Freeland said.
Last week Canada arrested Meng Wanzhou -- chief financial officer at Chinese telecom giant Huawei -- at the request of the United States, which plans to charge her with fraud charges related to sanctions-breaking business dealings with Iran.
China responded in kind, detaining the former Canadian diplomat, who is now a China expert at the International Crisis Group security consultancy.
Friends and experts say Kovrig may have become a "hostage" and "pawn" in a three-nation feud.
"In this case it is clear the Chinese government wants to put maximum pressure on the Canadian government," Guy Saint-Jacques, the former Canadian ambassador to Beijing, told AFP.
Wanzhou was released in Canada on strict bail conditions on Tuesday.
Ottawa said Chinese officials had been given consular access to Meng on December 1, contradicting claims by Beijing.