Hong Kong pro-democracy lawmakers say they'll press the government for answers after a fifth employee of a publisher specializing in books critical of China's ruling communists went missing.

Lawmaker Albert Ho said Sunday that the city is "shocked and appalled" by the disappearance of Lee Bo. Like the four others who disappeared late last year, he too is associated with publisher Mighty Current.

The company 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 is among those missing.

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