The Canadian foreign ministry identified the second Canadian as Michael Spavor.
China confirmed Thursday two Canadians are under investigation on suspicion of endangering the country's national security, fuelling tensions after Canada's arrest of a top Chinese telecom executive on a US request.
Former Canadian diplomat Michael Kovrig and business consultant Michael Spavor were put under "compulsory measures" on Monday, foreign ministry spokesman Lu Kang said, using a term which would ususally mean they are in custody.
The two Canadians are "suspected of engaging in activities that threatened China's national security," Lu said at a regular press conference, without explaining if the two cases are related.
Kovrig, who works for the International Crisis Group (ICG) think tank, was being investigated by the Beijing bureau of state security, while the agency's office in northeast Liaoning province was handling the probe into Spavor, Lu said.
Spavor is a China-based business consultant who facilitates trips to North Korea, met with its leader Kim Jong Un and arranged some of retired NBA star Dennis Rodman's trips to the country.
Their cases will fuel suspicions China is retaliating against Canada's arrest of Meng Wanzhou, the chief financial officer of Chinese telecom giant Huawei, at Washington's request on allegations related to breaking Iran sanctions.
Meng was released on Can$10 million (US$7.5 million) bail by a court in Vancouver on Tuesday pending a US extradition hearing.
Her case has infuriated Beijing and shaken Canada's relations with China, which is itself embroiled in a trade war with the United States.
Kovrig's employer, ICG, had reported his arrest earlier this week while Canada's government said on Wednesday that it had not heard from Spavor since he was questioned.
Lu said China provided "relevant information" to the Canadian consulate "without delay".
Kim and Rodman
Spavor is based in northeast China, where he runs the Paektu Cultural Exchange programme, an organisation that facilitates sport, cultural, tourism and business trips to North Korea.
He earned recognition after helping facilitate visits by former Chicago Bulls player Rodman in 2013 and 2014. Spavor is one of only a few Westerners to have met with Kim in recent years.
AFP's attempts to call his two mobile telephone numbers were met with messages saying "powered off" or "invalid" and calls to the Paektu Cultural Exchange office went unanswered.
"We have been unable to make contact since he let us know he was being questioned by Chinese authorities," Canadian foreign ministry spokesman Guillaume Berube told AFP.
Foreign Minister Chrystia Freeland said the Canadian government had raised his case with Chinese authorities.
Canadian officials said they were officially informed of Kovrig's detention via fax early Wednesday.
ICG has said that it has not received any information about Kovrig since his arrest.
China's foreign ministry said ICG was not registered in China and its employees would be "in violation" of the law if they engage in activities in the country.
"Canada is deeply concerned about the detention of Mr. Kovrig and Canada has raised the case directly with Chinese officials," Freeland said.
Kovrig was based in Hong Kong for ICG, working on foreign policy and security issues in the region, particularly on the Korean Peninsula.
ICG closed its office in the Chinese capital after Beijing passed a law on NGOs, which came into force in 2017, to better control the activities on its soil of foreign organisations.
Friends and experts say Kovrig may have become a "hostage" and "pawn" in the feud between China, the US and Canada.
Politicising extradition?
Freeland has also indirectly criticised statements by US President Donald Trump, who said in an interview on Tuesday he was ready to intervene in the Meng affair if it helped seal a trade deal with China.
"Our extradition partners should not seek to politicise the extradition process or use it for ends other than the pursuit of justice and following the rule of law," the Canadian minister said.
Asked by Reuters if he would intervene with the Justice Department in her case, Trump had been quoted as saying: "Whatever's good for this country, I would do."
Freeland said it would be "up to Ms Meng's lawyers whether they choose to raise comments in the US as part of their defence of Ms Meng."
It "will be up to the Canadian judicial process, to Canadian judges, how to weigh the significance of what Ms Meng's lawyers say."
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)