The family of a staffer at the UK consulate in Hong Kong have rejected a "made-up" report by Chinese state media that he was detained in the mainland for visiting prostitutes.
Simon Cheng disappeared after visiting the city of Shenzhen from the semi-autonomous city on August 8, and the Foreign Office in London said both British officials and relatives have been unable to speak to him since.
The Global Times, a tabloid state-run newspaper, said he had been detained for "soliciting prostitutes", citing police in Shenzhen, which lies on the China-Hong Kong border.
But a Facebook page run by Cheng's family dismissed the report.
"This is a made-up crime of soliciting prostitution, everyone should see it's a joke," the comment said.
Beijing confirmed Wednesday an employee of the British consulate had been "placed in administrative detention for 15 days as punishment" by police in Shenzhen for breaking a public security law.
"Let me clarify, this employee is a Hong Kong citizen, he's not a UK citizen, which is also saying he's a Chinese person," Chinese foreign ministry spokesman Geng Shuang said.
According to the Global Times, Cheng could be detained for up to 15 days and fined up to 5,000 yuan ($700) for the alleged crime.
In an editorial on Friday, the tabloid said it was at Cheng's request that police did not contact his family and that "thanks to the British foreign ministry and media, which have been hyping it, the case is now fully exposed."
Cheng was in the process of returning via high-speed train on August 8 and sent messages to his girlfriend as he was about to go through customs.
He has not been seen or heard from since.
The family said it had hired a lawyer in Shenzhen who had been unable to find or speak to the detained consulate employee.
Police in Shenzhen did not reply to AFP's request for comment.
A spokesperson for the British Foreign Office said in a statement Thursday that it was continuing "to urgently seek further information about Simon's case".
The incident comes as relations between Britain and China have become strained over what Beijing calls London's "interference" in pro-democracy protests that have wracked Hong Kong for three months.
China promised to respect the freedoms in the semi-autonomous territory after its handover from Britain in 1997 -- including freedom of speech, unfettered access to the internet and an independent judiciary -- but protesters say these rights are being eroded.
Chinese authorities have increased their inspections at the border since the protests, including checking the phones and devices of some passengers for photos of the demonstrations.
Beijing has faced criticism in the past for detaining foreign nationals amid ongoing diplomatic spats, and for accusing dissidents or activists of sex crimes.