Canada's foreign ministry says a third Canadian national has been detained in China.
The move threatens to escalate an already tense diplomatic feud between the two nations, which came after the arrest of a Chinese executive in Canada earlier his month.
Since then two Canadians have been detained in China, but Ottawa officials say they don't believe the third arrest is linked to those arrests.
Canadian Prime Minister Justin Trudeau expressed concern, saying more information is being collected.
Beijing's foreign ministry said it was unaware of the third arrest.