Hong Kong (CNN) 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.

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