A Canadian, reported to be a former diplomat, has been detained in China and his current employer says it is working for his prompt release.
The International Crisis Group said it was “aware of reports” of Michael Kovrig’s detention.
Prime Minister Trudeau said Canada is in direct contact with Chinese authorities concerning the case.
The news comes days after Canada arrested a top executive of the Chinese telecoms giant Huawei.
Mr Trudeau said the case is being taken “very seriously”. Canada’s foreign affairs ministry gave no further details about the incident or its talks with China.
Tensions between Canada and China have been high over the arrest of Meng Wanzhou, Huawei’s chief financial officer and daughter of its founder, on Saturday 1 December.
Federal public safety minister Ralph Goodale told journalists in Ottawa that the government is “deeply concerned by the situation”.
The minister said there is currently no “explicit indication” of any link between her arrest and Mr Kovrig’s reported detention.
Mr Kovrig had previously worked as a diplomat in Beijing, Hong Kong and at the UN in New York.
Mr Kovrig has been working since February 2017 as North East Asia senior advisor for the International Crisis Group, a Brussels-based think tank that focuses on conflict reduction research.
He worked with Canada’s foreign affairs ministry between 2010 and 2016 and was posted in Hong Kong and Beijing between 2012 and 2016.
Ms Meng faces extradition to the US on charges of fraud related to sanctions-breaking business dealings with Iran.
She could be jailed for up to 30 years if found guilty.
China has demanded that Canada release Ms Meng or face consequences.
She is scheduled to appear on Tuesday in the Supreme Court of British Columbia for the third day of her bail hearing.
Her husband has offered C$15m ($11m; £9m) – C$1m in cash and the couple’s two homes in Canada – as surety for Ms Meng’s release.
Canadian Crown prosecutors have asked for bail to be denied because they believe the wealthy executive poses a flight risk.
China’s foreign ministry also insisted on Tuesday that Canada failed to promptly notify Beijing immediately about Ms Meng’s arrest, according to a state media report.