The Associated Press

Hong Kong pro-democracy lawmakers said Sunday that they will press the government for answers after a fifth employee of a publisher specializing in books critical of mainland China's leadership went missing.

Lawmaker Albert Ho said the city was "shocked and appalled" by the disappearance of Lee Bo. Like the four others who disappeared in recent months, Lee is associated with publisher Mighty Current.

While there's been no official confirmation on the status of the five missing people, Ho told reporters that it appears their disappearances are linked to the company's books.

"From the available information surrounding the disappearance of Mr. Lee Bo and his partners earlier, we have strong reason to believe that Mr. Lee Bo was probably kidnapped and then smuggled back to the mainland for political investigation," Ho said.

Mighty Current and its Causeway Bay Bookstore are known for gossipy titles about Chinese political scandals and other sensitive issues that are popular with visiting tourists from the mainland. The company's co-owner, Gui Minhai, is among those missing, as are three staff members.

Books by Mighty Current are banned on the mainland but available in Hong Kong, which enjoys freedom of the press and other civil liberties unseen on the mainland because of its status as a specially administered region of China. However, the disappearances highlight growing concern that Beijing is moving to tighten its grip on the former British colony.

Hong Kong Acting Secretary for Security John Lee told reporters that police were "actively" investigating the case.

Lee went missing Wednesday evening and was last seen leaving his company's warehouse, according to local media reports.

His wife told the Cable TV news channel in a report broadcast Saturday that she received a phone call from him the night he disappeared. She said he told her then that he was "assisting an investigation" and alluded to the earlier disappearances, but was not more specific.

The number indicated the call came from Shenzhen, the mainland Chinese city next door to Hong Kong, the report said.