THE Foreign Office has said it is “urgently” seeking more information about a British Consulate worker detained in China.

Simon Cheng Man-kit, who works at the British Consulate-General in Hong Kong, was given 15 days of administrative detention after crossing the border on August 8.

A spokesman for the Foreign and Commonwealth Office said officials had been unable to contact Cheng since.

The spokesman said: “We continue to urgently seek further information about Simon’s case. Neither we nor Simon’s family have been able to speak to him since his detention.

“That is our priority and we continue to raise Simon’s case repeatedly in China, Hong Kong and London, and have sought to make contact with Simon himself.”

China said Cheng was detained in the city of Shenzhen for violating regulations on public order.

His detention comes after weeks of pro-democracy protests sparked by a now-suspended bill which would have allowed extraditions from Hong Kong to China.

Tensions remain high as mass demonstrations continue, with protesters criticising both the Hong Kong and Chinese governments.

Chinese Foreign Ministry spokesman Geng Shuang said at a daily briefing: “The relevant employee is a Hong Kong resident, not a British citizen. In other words, he is Chinese. This is purely the internal affairs of China.”

Geng said Cheng had violated regulations on “Punishments in Public Order and Security Administration” but gave no further details, adding that his case is “not a diplomatic issue”.

Public order and security infractions are generally minor – for instance, fighting in the street – and result in administrative rather than criminal punishments. The maximum penalty is 15 days in detention.

The case has stoked fears among Hong Kong residents that Beijing is extending its judicial reach to Hong Kong, a semi-autonomous Chinese territory and former British colony.

About two dozen people gathered on Wednesday outside the British consulate in Hong Kong to demand the UK Government step up efforts to secure the release of Simon Cheng Man-kit, a trade and investment officer at the consulate.

“Save Simon now!” the crowd chanted in front of a wall of missing person posters with pictures of Cheng.

Max Chung, the event’s organiser and an acquaintance of Cheng, said he had travelled to the neighbouring city of Shenzhen on a mainland travel permit for Hong Kong and Macao residents.

He holds a British National Overseas passport, according to Chung. The travel document is issued by the UK to Hong Kong permanent residents.

Chung and other friends of Cheng said they believe he was detained at the high-speed railway station in West Kowloon, part of Hong Kong. The station stirred controversy ahead of its opening last September because passengers go through Chinese immigration and customs inside it.

Mainland law applies in the customs area, sparking concerns among Hong Kongers over the ability of mainland authorities to enforce Chinese law on Hong Kong soil. Some said this is a breach of the “one country, two systems” framework, which allows Hong Kong to largely run its own affairs until 2047.