Hong Kong Missing Bookseller Lee Bo, China
Missing Hong Kong book publisher Lee Bo's wife met her husband on the mainland, the Hong Kong police said Saturday. Pictured: People take part of a rally on Jan. 10, 2016, in Hong Kong, protesting against the missing booksellers, who are suspected to have been taken into custody by Chinese officials. Getty Images/Lam Yik Fei

The wife of a missing editor of a Hong Kong publishing firm told Hong Kong police that she has met him in mainland China, the Associated Press reported Saturday. British citizen Lee Bo and four of his colleagues -- whose books were critical of the Chinese government and were banned in the mainland -- disappeared late last year, sparking fears that Beijing was clamping down on Hong Kong's freedom of speech.

Hong Kong police said in a statement that Lee’s wife had met him on Saturday afternoon at a guesthouse on the mainland. Lee looked healthy and in good spirits, she reportedly said, adding that he told her he was assisting in an investigation as a witness.

After his disappearance Lee had written in letters to his wife that he had traveled to mainland China of his free will but his supporters believe that he was kidnapped and smuggled by Chinese security agents. Lee was last seen at his company warehouse on Dec. 30 and did not have his mainland travel permit. However, days after going missing, he reportedly called his wife to say he was in Guangdong.

Lee and the four other disappeared men are linked to Hong Kong publishing company Mighty Current and its Causeway Bay Bookshop, which prints and sells tittles on Chinese political intrigue that Beijing has banned on the mainland.

Lee’s wife also handed over a letter from Lee addressed to the Hong Kong police. The police statement said its content was similar to his previous letters, AP reported. It is still unclear what investigation Lee and the other four men are involved in and whether Lee was detained or assisted Chinese police voluntarily.

Hong Kong police reportedly said that Lee’s case was still under investigation and that they had again asked police in Guangdong province, over the mainland border, to assist in arranging a meeting with Lee.

The disappearance sparked protests in Hong Kong over Chinese censorship extending to Hong Kong in breach of the "one country, two systems" principle Beijing promised to uphold after taking control of the city from Britain in 1997. Following the event, many Hong Kong booksellers and publishers removed politically sensitive books from their shops.