Three stowaways were found aboard a cargo ship from the Dominican Republic that pulled into the Port of Charleston on Saturday.
One of them was dead in a container.
There was no indication the stowaways were a threat, but officials said they took the breach seriously.
The M/V MSC Debra left the Dominican Republican on Wednesday and arrived at the Wando Welch Terminal at noon Saturday, according to Brian Welch, a local supervisor with U.S. Customs and Border Protection.
The three men made the three-day trip hiding in a container. A hole had been cut in the top of the container to let in air and allow them to enter and leave.
Dockworkers unloading the ship reported seeing men climbing out of a container Saturday afternoon. A joint team from Border Protection and the Coast Guard responded.
Crew members captured one of the stowaways on the ship. Coast Guard officers pulled the other from the water after he jumped off the ship.
A third man was found dead in the container. The Charleston County Coroner's Office had not determined the cause of death nor released the man's identity Sunday.
The ship left the terminal early Sunday morning.
"This type of incident is a clear indication of the risks people are willing to take to illegally enter the United States," Robert A. Fencel, the area port director in Charleston for Customs and Border Protection, said in a statement. "While the loss of life is truly regrettable, the joint efforts of local, state and federal agencies helped bring this incident to a successful conclusion while ensuring the safety of both the maritime industry and the community."