What unit of the Immigration Bureau immigrated to Hong Kong?

In fact, the Hong Kong Immigration Department is not responsible for border inspection. The customs is responsible for the border inspection in Hong Kong, the Immigration Department is responsible for visas, and some nationality and immigration issues are handled. Simply put, it is to manage the activities of non-Hong Kong residents in Hong Kong. For example, whether or not to let you enter Hong Kong is the decision of the Immigration Department, but even if you can't get in, it doesn't matter how you get in and what you bring in. The latter is the responsibility of the customs. Therefore, don't think that the Hong Kong Immigration Department is a border inspection. Actually, it is not. It's the Hong Kong Immigration Department. It is just called the Immigration Department, and its work is still the work of the Immigration Department.

Immigration offices in western countries will not be responsible for border inspection. Generally, border inspection is handled by customs, which is similar all over the world, and so is China. If the customs finds some illegal immigrants, they will be handed over to the immigration bureau, which will be responsible for repatriation. Entry involves many institutions, not just immigration or customs or others.