The mystery surrounding five missing Hong Kong booksellers known for titles banned in mainland China deepened after one purportedly wrote a letter saying he was fine and helping with an investigation on the mainland, prompting his wife to drop a missing person's report.
Hong Kong police said Lee Bo's wife cancelled the report but they would continue investigating the other disappearances. Their statement did not say whether Mr Lee had been located.
The UK Foreign Office confirmed by email that one of the missing booksellers is British, and Hong Kong media report it is Mr Lee. The email said Britain was "deeply concerned" about the case and has "urgently requested" help from local authorities for information on the individual.
Five people who vanished since October are associated with publisher Mighty Current, which specialises in books critical of China's Communist Party leaders.
When Mr Lee vanished last Wednesday, he reportedly did not have a travel permit for mainland China with him, triggering speculation he did not plan to go there and that Chinese security agents abducted him. The four others were last seen either in mainland China or Thailand.
An image of Mr Lee's handwritten letter was published by Taiwan's government-affiliated Central News Agency late on Monday and subsequently by Hong Kong media.
The letter, faxed to an employee at the publishing company's Causeway Bay Bookstore in Hong Kong, said: "Due to some urgent matters that I need to handle and that aren't to be revealed to the public, I have made my own way back to the mainland in order to cooperate with the investigation by relevant parties."
"It might take a bit of time," it said. "My current situation is very well. All is normal."
The letter gave no details on the investigation to which it refers.
Hong Kong police still have missing person's files open for three other staff members or shareholders of the publisher or the book store. One of the publishing company's owners, Gui Minhai, is a Swedish national who went missing in Thailand in October, according to Hong Kong media and human rights groups.
Swedish foreign ministry spokesman Joakim Edvardsson said on Monday the government was "very concerned" about the disappearance of one of its citizens.
Hong Kong media reported that Mr Lee's wife, Choi Ka-ping, asked police to drop the missing person's report after learning of the letter, the authenticity of which could not be independently confirmed.