Since the reform and opening-up, Hong Kong and the mainland have had increasingly frequent exchanges. This has led to several law-and-order problems involving criminal activity across the two regions, most notably smuggling, drug trafficking, theft, robbery, and hostage-taking. Some criminals from Hong Kong commit crimes on the mainland or flee there after committing crimes in Hong Kong. Others from the mainland commit crimes in Hong Kong or flee there after offending on the mainland. There are also criminals from both regions who collude to commit crimes together.
