Secret Service Agent John Kenny in Charleston says a search warrant was issued for the container Monday night. Kenny says it was about the size of a cooler.
Firefighters and officials from the Department of Health and Environmental Control were also called to the scene.
DHEC spokesman Mark Plowden says agency workers turned the case over to law enforcement. Authorities would not comment on what was inside.
But Plowden says there was never any threat to public health.