Canada’s foreign ministry says it is trying to make contact with a second Canadian who is believed to have been detained in China.
Michael Spavor, a businessman based in Dandong near the North Korean border, had contacted Canadian officials this week to say he was being questioned.
Foreign ministry spokesman Guillaume Bérubé said Canada was working hard to determine Mr. Spavor’s whereabouts.
It comes after former diplomat Michael Kovrig was arrested in China this week.
Mr. Kovrig currently works for a think thank, the International Crisis Group (ICG), which has said it is concerned for his health and safety.
At a news conference in Ottawa on Wednesday, Foreign Minister Chrystia Freeland said Mr. Kovrig’s case had been raised directly with Chinese officials.
She also said a second Canadian had contacted them earlier in the week because “he was being asked questions by Chinese authorities”.
She did not name the individual, saying it was “delicate situation” and she wanted to respect his privacy.
But Mr. Bérubé later named the man in a statement as Mr. Spavor and said he was “presently missing in China”.
China state media confirmed on Thursday that, as with the previous arrest, Mr. Spavor was under investigation on suspicion of “engaging in activities that endanger China’s national security”.
Mr. Spavor runs an organisation called Paektu Cultural Exchange, which organises business, culture and tourism trips to North Korea.
He is a regular visitor to North Korea and regularly comments in the media on Korean issues. He is particularly well known for helping to arrange the visit by former NBA star Dennis Rodman to North Korea in 2013.
Rodman is a personal friend of North Korean leader Kim Jong-un.
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His last tweet, on Sunday, said he was about to travel to Seoul in South Korea, but he did not arrive on Monday as planned.
The detentions have come after Canada arrested Chinese telecoms executive Meng Wanzhou last week.
Ms. Meng is the chief financial officer of Huawei, one of China’s biggest telecoms companies, and the daughter of its founder.
She was arrested at the request of the US and is accused of violating sanctions on Iran. She was granted bail on Tuesday for C$10m (£6m; $7.4m) bail but could be extradited to the US.
China has demanded that Canada release Ms Meng, and has threatened unspecific consequences.