According to Lt. Zorn with the Coast Guard, investigators as of Thursday morning had zero credible information to suggest there is a “dirty bomb” aboard the Memphis. Lt. Zorn reiterated that agencies are investigating the threat out of an overabundance of caution.
Lt. Zorn also said Thursday Coast Guard personnel in major ports such as Charleston are outfitted with radiation detection devices. Lt. Zorn says results are not yet available from a radiation sweep aboard the Memphis by Coast Guard Sector Charleston.
http://abcnews4.com/news/local/wando-welch-port-terminal-evacuated-for-threat
Yep... this is like the classic calling in bomb threats to schools, just a lot more expensive in terms of manpower needed to clear it and disruption to the port operations.
Since the threat came via YouTube, I would think the Feds should be able to track down its source... at least if it came from within the US.