Which agency is responsible for first-line seizures of contraband at the border?

The agency responsible for first-line seizures of contraband at the border is Customs and Border Protection (CBP). CBP has the primary mission of protecting national borders and ensuring the security of trade and travel while enforcing U.S. laws. This includes preventing the smuggling of illegal goods, contraband, and substances into the country. Agents from CBP are stationed at various points along the border and are specifically trained and equipped to perform inspections and take action when they detect or suspect contraband.

Due to its dedicated role at the border, CBP is the first point of contact for any contraband-related issues, making it the most appropriate choice in this scenario. The other agencies mentioned, while they have important roles in law enforcement and border security, do not have the same front-line responsibility for initial contraband seizures at the border as CBP does.