Maybe they were Civil War buffs, on their way to reenact the attack on Fort Sumter.

"Vehicle with explosives stopped in US," from [1] Deutsche Presse Agentur (thanks to rocketsbrain):

Washington (dpa) - Local police outside Charleston, South Carolina stopped a vehicle in which they found what were suspected to be explosives, according to media reports late Saturday.

Two men described as being of possibly Middle Eastern origin were in the vehicle, which was stopped on a highway. A police bomb squad was at the scene and preparing to examine the vehicle, a local television reported told the Cable News Network (CNN).