The Public Security Department in Mainland China’s Guangdong Province has released a statement to the Hong Kong Police Force confirming that the remaining 3 missing bookseller are in their custody. A statement from the Hong Kong police said that the 3 men are being held in relation to a case involving another bookseller named Gui Minhai.

In total 4 booksellers are currently being held for criminal activity, with another ‘assisting’ in the investigation, all 5 men are connected to the Hong Kong publishing company “Mighty Current Media”. Gui, a co-owner of the company, is reportedly being held on a drunk driving charge from 11 years earlier, which apparently resulted in the death of a women.

The company has been known to publish books highly critical of the Mainland Communist government. Works go into personal details of politicians sex lives, as well as instances of corruption. Works by the company have been banned by the Mainland government, but in Hong Kong, which has a range of liberties that the mainland does not, they are incredibly popular.

The arrests of the booksellers has lead many to believe that Mainland China is attempting to tighten its control over Hong Kong.