HONG KONG -- The wife of a missing chief editor of a publisher specializing in books banned in mainland China has told police she has been able to visit him on the mainland, Hong Kong police said Sunday.

It is the latest twist in the disappearances of British citizen Lee Bo and four of his colleagues that have intensified fears that Beijing is clamping down on Hong Kong's freedom of speech. Lee has previously written that he returned voluntarily to mainland China in letters to his wife, but his supporters believe he was kidnapped and smuggled to the mainland.

Hong Kong police said in a statement Sunday that Lee's wife had told them she had met him on Saturday afternoon at a guesthouse on the mainland. She said he was healthy and in good spirits, and that he was assisting in an investigation as a witness. She gave no further details regarding the location of the meeting or the nature of the investigation.

She also handed over a letter from Lee addressed to Hong Kong police. The police statement said its content was similar to his previous letters.

The latest development raises more questions than it answers. It is still unclear where Lee and the other four men linked to Hong Kong publishing company Mighty Current and its Causeway Bay Bookshop are exactly, what the investigation involves, and whether Lee is detained or there voluntarily, as he has purportedly said in his letters.

Hong Kong police said they are continuing to investigate Lee's case and had again asked police in Guangdong province, over the mainland border, to assist in arranging a meeting with Lee.

The circumstances of Lee's case have led many to suspect Chinese security agents crossed into Hong Kong to abduct him, in breach of the "one country, two systems" principle Beijing promised to uphold after taking control of the city from Britain in 1997. According to local news reports, he was last seen at his company's warehouse on Dec. 30 and didn't have his mainland travel permit, but days after he went missing he called his wife to say he was in Guangdong.

The other four men have disappeared since October from mainland China or Thailand.

Mighty Current specialized in racy but thinly sourced titles on Chinese political intrigue and scandals and other topics Beijing deemed off limits for mainland Chinese publishers.