A staff member at the British consulate in Hong Kong has been given 15 days of administrative detention in the Chinese city of Shenzhen, China said.
At a daily briefing on Wednesday, foreign ministry spokesman Geng Shuang offered no details about why he was being detained.
The British Foreign Office had said it was “extremely concerned” about its staff member, identified as Simon Cheng Man-kit, who attended a business event in Shenzhen on August 8 but never returned to neighbouring Hong Kong despite plans to do so the same day.
When Mr Cheng failed to return to work, his family, including his girlfriend Li, informed the police.
Li, who met Mr Cheng when they were both studying in the UK, told news outlet HK01 that he had contacted her shortly before the border crossing.
She shared screenshots of messages from Mr Cheng on WeChat, which is believed to be monitored by the Chinese government, as well as a conversation on WhatsApp.
“Ready to pass through the border,” one WhatsApp message read. Mr Cheng added: “Pray for me.”
Mr Cheng then added in a message on WeChat: “Passing through, pray for me.”
It has also been reported by HK01 that he told colleagues during the business trip to delete WeChat before they crossed the border back into Hong Kong.
Mr Cheng’s disappearance came after weeks of pro-democracy protests sparked by a now-suspended bill that would have allowed extraditions from Hong Kong into China.
It is unclear whether he possessed a diplomatic passport and Mr Geng said he was a Hong Kong resident.
It is believed that, although he works for Scottish Development International, Mr Cheng is employed by the British Consulate-General in Hong Kong.
Tensions remain high as mass demonstrations continue with protesters criticising both the Hong Kong and Chinese governments.