Canada says it is seeking consular access as soon as possible to a former Canadian diplomat who has been detained in China.
Michael Kovrig was held on Monday by the Beijing National Security Bureau.
His current employers, the International Crisis Group (ICG), say they are concerned for his health and safety.
Canadian officials say the reason for his detention remains unclear.
They do not know where he is being held.
Canadian Foreign Minister Chrystia Freeland said on Wednesday the case has been raised directly with Chinese officials.
News of Mr Kovrig's detention came days after Canada arrested Chinese telecoms executive Meng Wanzhou.
Ms Meng, Huawei's chief financial officer, was released in Vancouver, Canada on Tuesday on C$10m (£6m; $7.4m) bail.
She was arrested on 1 December and could be extradited to the US to face fraud charges linked to the alleged violation of sanctions on Iran.
China has demanded that Canada release Ms Meng or face consequences.