HONG KONG (AP) — The chief editor of a Hong Kong publisher of books banned in mainland China who disappeared three weeks ago has been located in the mainland, Chinese officials told Hong Kong authorities.

Lee Bo, a British citizen, is one of five men linked to Hong Kong publishing company Mighty Current and its Causeway Bay bookshop who have gone missing in recent months. The cases have gripped the semiautonomous Chinese city and sparked fears Beijing is clamping down on the city's freedom of speech.

Hong Kong police said late Monday that they received notice from Guangdong province's public security department that Lee was "understood" to be in the mainland.

Lee's case in particular raised alarm bells because it raised suspicions that Chinese security agents crossed into Hong Kong to abduct him. According to local news reports, he was last seen at his company's warehouse and did not have his travel permit for mainland China with him, but days after he went missing he called his wife to say he was in Shenzhen, the city next to Hong Kong.

Police said in a brief statement that Guangdong officials also forwarded to them a letter from Lee to the Hong Kong government, with handwriting that Lee's wife confirmed was his. Police said the letter was similar to one Hong Kong media reported on Monday, which he purportedly wrote to his wife to tell her he "voluntarily" went to the mainland to assist authorities with an investigation, details of which he didn't disclose.

The news came a day after another of the five missing men, Swedish national Gui Minhai, was shown on state TV tearfully confessing that he turned himself in to mainland authorities over a hit and run accident that he was involved in a decade ago. However, human rights activists said they suspected Gui was forced to make the confession.