With the case garnering considerable international attention, the suspicion remains that Lee was abducted by Chinese police and that he was pressured by the Chinese authorities into sending the fax. On Monday, his wife, Sophie Choi, went to Hong Kong police to withdraw her earlier complaint, according to Hong Kong's Ming Pao newspaper.
"I think it's a charade performed under duress," said Claudia Mo, a legislator with the pro-democracy Civic Party.
"He has obviously been smuggled out, but his wife has got the message that keeping a low profile would help his release, because the Chinese would save face."
Lee's disappearance was seen as an assault on Hong Kong's cherished principles of freedom of expression and autonomy from Beijing, as well as a sign that China is becoming increasingly bold in its efforts to track down and abduct dissidents and opponents outside its borders.
Hong Kong's chief executive, Leung Chun Ying, said it was "not acceptable" for Chinese police to operate independently in Hong Kong, but Leung, a Beijing loyalist, said there was "no indication" that this was what had happened.
Pro-democracy politicians said, however, that it appeared likely Lee had been kidnapped by Chinese police.
If confirmed, legislators said, Lee's abduction would be a serious violation of the "one country, two systems" principle and the Basic Law framework that has defined Beijing's relations with Hong Kong since the 1997 handover from British rule.
Lee, a major shareholder in Mighty Current and subsidiary Causeway Bay Books, disappeared from Hong Kong, before reportedly calling his wife from a number in Shenzhen, southern China, saying he was assisting in an investigation.
In October, the company's major shareholder, Gui Minhai, disappeared from his beachfront apartment in Thailand, while three employees vanished around the same time while travelling in southern China.
Democratic Party lawmaker Albert Ho said t one possible explanation for Lee's disappearance was that the Mighty Current publishing company was being pressured to scrap plans for a book rumoured to be about an old "girlfriend or mistress" of Xi.
Willy Wo-lap Lam, an adjunct professor at the Chinese University of Hong Kong, said the book was to have been titled The Lovers of Xi Jinping and would have covered the period when Xi held various official posts in Fujian province between 1985 and 2002, including after his marriage to well-known People's Liberation Army singer Peng Liyuan in 1987.
- Washington Post, Bloomberg