The other two Canadians - Michael Kovrig, a diplomat on leave, and Michael Spavor, an entrepreneur who works throughout Asia and makes frequent trips to North Korea - were arrested by the Chinese government because of "national security" concerns.
President Donald Trump complicated matters by saying he might intervene in the case if would help clinch a US trade agreement with China - much to the consternation of Canadian officials who said the arrest was not political and they were just following their extradition treaty obligations.
One person said McIver was expected to be returned before the New Year.
When China responds to criticism of the Kovrig/Spavor detentions by raising the Meng case, that is an admission that it's all about retaliation.
China has accused the other Canadian detainees of activities "that endanger China's national security".
This TV image provided by CTV to AFP shows Huawei Technologies Chief Financial Officer Meng Wanzhou as she exits the court registry following the bail hearing at British Columbia Superior Courts in Vancouver, British Columbia, Dec. 11, 2018. Obviously, if there were no connection, those who object should no more reflect on Canada's actions than they should reflect on the actions of, say, Saudi Arabia.
Citing anonymous sources, Canadian outlet the National Post reported that the detainee is an Alberta woman named Sarah McIver, who had been teaching at a school in China before being taken into custody due to visa complications.More news: Russia's High-Tech Robot Is Just a Man in a Suit
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"Escalation or very strong political statements can actually end up being counterproductive to", Trudeau said, noting political posturing or statements are not necessarily going to help those detained. The Canadian authority did not confirm a timeline to the news site.
The risk, he said, is that other countries are also being "pulled in to this increasingly toxic relationship between the world's two biggest economies".
Trudeau said he was asking China for more information on the detentions.
Canadian PM Justin Trudeau has said he is "very concerned" about a third Canadian detained in China.
"In China there are no coincidences".
China has demanded Meng's immediate release and summoned in the Canadian and US ambassadors to complain about the case.
While no link between the latest arrest and the first two has yet been established, the arrests are widely seen as retaliation for the detention of Huawei executive Meng Wanzhou at a Vancouver airport December 1.
She is due in court on February 6.
Meng was released on bail last week in Vancouver pending a United States extradition hearing on USA fraud charges related to sanctions-breaking business dealings with Iran. On December 14, Wanzhou was released on bail; the stir her arrest has created is larger than one could have anticipated and according to CNBC, "it immediately hit U.S. stocks and sent global markets into a tailspin".