Which office provides vital information regarding the status of detainees?

The On-line Detainee Locator System is the correct choice because it is specifically designed to help individuals and organizations find information regarding the location and status of immigration detainees held by U.S. Immigration and Customs Enforcement (ICE). This system allows users to search for detainees using their personal details, which is essential for family members, legal representatives, and others who need to track the status and whereabouts of someone detained under immigration laws.

In contrast, the other options serve different purposes. The Office of Immigration Litigation focuses on representing the U.S. government in court cases related to immigration law, rather than providing real-time detainee information. The Office of Citizen Services deals primarily with providing assistance and information to U.S. citizens, not specifically related to detainee status. The Office for International Affairs manages international relations and does not directly handle detainee information either. Thus, the On-line Detainee Locator System is uniquely positioned to provide the vital information sought in this context.