HONG KONG (Reuters) - The wife of one of five missing Hong Kong booksellers said she met with her husband in China, according to a statement released by the Hong Kong police on Sunday amid growing diplomatic pressure on Chinese authorities to clarify the fate of the men.

Members from the pro-democracy Civic Party carry a portrait of Lee Bo (L) and Gui Minhai before they protest outside Chinese Liaison Office in Hong Kong, China January 19, 2016. REUTERS/Bobby Yip

Lee Bo, 65, an owner of a publisher and bookshop specializing in books critical of China’s Communist Party leaders, vanished in late December amid widespread speculation that Chinese authorities may have abducted him in the financial hub and spirited him across to China for an investigation.

Lee, who has dual Hong Kong and British citizenship, surfaced on Saturday, meeting wife at a guesthouse in mainland China, the Hong Kong police said in a statement issued after midnight on Sunday.

His wife, Sophie Choi, told police that she had met with her husband at a guesthouse in China on Saturday and that he was healthy and in good spirits.

The statement cited Lee’s wife as saying he was “assisting in an investigation in the capacity of a witness,” though she didn’t give specifics on the location nor the nature of the investigation, the statement added.

The Hong Kong police said they would continue to probe the case, and would put in a fresh request with police in China’s southern Guangdong province to arrange a meeting with Lee Bo.

Calls to the mobile phones of Lee and his wife went unanswered.

The disappearances have prompted fears that mainland Chinese authorities may be using shadowy tactics that erode the “one country, two systems” formula under which Hong Kong has been governed since its return to China from British rule in 1997.

One of the missing men, Gui Min-hai, a Swedish passport-holder, appeared on China state television last weekend, saying he had voluntarily turned himself in to Chinese authorities over a fatal drink-driving offense more than a decade ago.

So far, Chinese authorities have not responded to multiple requests for comment from Reuters, nor have they made any substantial statements explaining Beijing’s role in the disappearances nor the fate of the men.

Earlier this month, thousands took to the streets of Hong Kong demanding to know the whereabouts of the men who were all linked to a publisher that was reportedly planning a new book on the private life of Chinese leader Xi Jinping.

A senior foreign diplomatic source in Hong Kong with direct knowledge of the matter said at least six foreign governments had now officially pressed China for information regarding the disappearances, but so far there had been a “deafening silence”.

The source who declined to be named given the sensitivity of the case, said the “suspicious circumstances suggested a rendition of one of the disappeared persons” by China.

Publishers and book vendors in the city have also been unnerved by the mysterious disappearances, and in some cases pulled books critical of Beijing’s leaders from their shelves.