The British government is seeking answers from China about a staff member from its consulate in Hong Kong who, according to his girlfriend, has been detained across the border for at least 10 days. Simon Cheng Man-kit’s girlfriend, a 27-year-old Taiwanese working in Hong Kong who asked to be identified only by her surname, Li, said the 28-year-old disappeared on August 8 while returning home through the immigration checkpoint at the West Kowloon terminus of the cross-border high-speed railway linking the city to Shenzhen and Guangzhou. The British consulate said it was “extremely concerned by reports that a member of our team has been detained returning to Hong Kong from Shenzhen”. “We are providing support to his family and seeking further information from authorities in Guangdong province and Hong Kong,” a spokesman said. Chinese foreign ministry spokesman Geng Shuang denied knowledge of the case, while mainland public security officials with jurisdictional authority in their designated zone at the terminus said they had not made any arrest that day. A mainland-based lawyer hired by Cheng’s family could not find any record of him in any detention centre in Shenzhen or Guangzhou. Under the so-called co-location arrangement, the zone beyond the Hong Kong immigration checkpoint at the railway station is a mainland port area, where China’s national laws are fully applicable. While Hong Kong’s Immigration Department would not comment on the case, Li said Cheng’s family had been informed by the department that he had been placed under “administrative detention”, which would mean he could be held for 15 days before a criminal investigation is launched. Hong Kong police confirmed on Tuesday that they received a missing-person report about Cheng on August 9, but had not received any notification from mainland authorities. A notification mechanism between Hong Kong and the mainland regarding such cases does not cover administrative detention. A police spokesman said the force had “maintained close contact with relevant authorities on the mainland”. “At first I didn’t want his case to go public because I was worried exposure would further jeopardise him,” Li told the Post . “But now I really don’t know what else I can do.” Born in Hong Kong and educated in Taiwan and London, Cheng has held the title of trade and investment officer of Scottish Development International at the British consulate in Hong Kong since late 2017. Hongkonger detained in Macau over anti-government protests rally He left for Shenzhen, the mainland city just across the border from Hong Kong, on a one-day business trip on August 8, Li said, and sent his last text message to her at 10.42pm that night on his way back to Hong Kong. She said he had written “passing through”, following two earlier messages, one letting her know he was on a cross-border train at 10.37pm, and another saying he was ready to clear customs at 10.40pm. Calls to Cheng’s mobile phone went unanswered after that, she said. Li and Cheng’s elder sister notified the consulate the next day and followed the consulate’s advice to file a report to Hong Kong police and immigration authorities. On August 10, the Immigration Department and the consulate separately confirmed to Cheng’s family that he was being detained, but had no further details, Li said. According to Cheng’s family, an investigator assigned to the case from the West Kowloon police region informed them on August 11 that he was unable to get further details. Cheng’s elder sister and Li wrote to British Consul General Andrew Heyn, urging him to help hire a lawyer on the mainland for the missing man. “Seriously, our family does not have the appropriate knowledge and financial ability to seek any assistance,” the elder sister wrote in her letter dated August 11. Several refused entry to Hong Kong as groups of men cross border, source says But Li said that, in a meeting the next day, the consulate rejected the family’s request for legal assistance, saying that was not their responsibility since Cheng had gone missing while off-duty. According to Cheng’s family, the Hong Kong Economic and Trade Office in Guangzhou, from which the Immigration Department learned about his detention, refused to disclose to them which mainland authority had notified them in the first place, citing “privacy issues”. When asked if Cheng had taken part in the anti-government protests sweeping Hong Kong, Li said they had not done so together, but she was not sure whether he had joined any on his own. Responding to inquiries from the Post earlier, the British foreign office said it was concerned that a staff member had been reported missing. “We are in contact with authorities in Guangzhou and Hong Kong and seeking further information,” a spokesman said.