A package that was going to be loaded onto a cruise ship at the Port of Miami tested positive for plastic explosives Monday, the Coast Guard said.
The package was tested six times, and each time, it came back positive for C4, said Petty Officer James Judge.
Miami-Dade police were examining the package to confirm whether explosives were present.
The developments came a day after three Middle Eastern men in a cargo truck sparked a brief terrorism scare at the port. After a bomb squad search, authorities concluded that the men were carrying automotive parts and that the scare had stemmed from miscommunication.