They say the brain was in an international mail shipment at Blue Water Bridge in Port Huron.
Officers stopped a Canadian mail truck for an inspection. During the routine mail operation, they say they came across a shipment manifested as an "Antique Teaching Specimen".
Upon opening the shipment, CBP officers found the package to contain a human brain specimen inside of a clear glass mason jar without any paperwork or documentation.
The shipment from Toronto, Canada was headed for Kenosha, Wisconsin.
The brain specimen is being investigated by the CDC for any potential infectious biological agents, infectious substances, and a decision on what to do with the specimen.