Bloomberg has an editorial by Admiral James Stavridis, USN (retired), former United States Southern Command (2006 to 2009) and commander, United States European Command and NATO Supreme Allied Commander Europe (2009 to 2013) that suggests the smugglers’ methods now increasingly include shipping by container in otherwise legal shipping. He goes on to suggest some possible countermeasures.
Surprisingly there is no mention of Fentanyl which appears to be an emerging drug of choice. Fentanyl is still primarily a prescription drug abuse problem, but that may be changing. Its strength in even very small quantities makes it an almost ideal drug for smuggling.