In all seriousness, I think you will find these are either drug dealers or people sending them overseas for their families to sell.
What we are starting to see is the “See something, say something” wave starting. This type of stuff has been going on for decades (in general terms) and no one cared.
Well, let’s hope you are right, but then the missing propane tanks must also be part of the drug trade. We all know that no jihadi would ever think of putting the two together to make a barrel bomb ... certainly not a Syrian refugee ...