The United Kingdom Foreign Office is "extremely concerned" by reports that a British Consulate staff member in Hong Kong has been detained in mainland China for over 10 days.

The British Consulate-General in Hong Kong on Tuesday addressed local media reports that Simon Cheng has been held in Shenzhen, a city on Hong Kong’s border with mainland China, since August 9.

“We are extremely concerned by reports that a member of our team has been detained returning to Hong Kong from Shenzhen,” a spokesperson for the UK Foreign and Commonwealth Office said in an email Tuesday.

“We are providing support to his family and seeking further information from authorities in Guangdong province and Hong Kong,” the spokesperson added.

The British Embassy in Beijing put out an identical statement.

At a press conference Tuesday, a spokesperson for the Hong Kong Police said the force had not been contacted by mainland Chinese authorities regarding a missing British consulate worker.

Senior Superintendent Kong Wing-cheung did confirm, however, that the police had received a missing person report on August 9, but could not disclose more details. “The case is currently under inquiry by the regional missing person unit of Kowloon West region,” he added.

In a statement, Hong Kong Immigration Department said it had received a request for assistance from Cheng’s family. The department said it had contacted the Hong Kong Economic and Trade Office in Guangdong for information and was providing Cheng’s family with advice and assistance.

At a press conference Tuesday, China’s Ministry of Foreign Affairs spokesman Geng Shuang said he was “not aware of the situation.”