According to the Times Online (UK), the two men picked up on suspicion of terrorism for having ordered and received large quantities of petroleum-based fuel were not, after all, buying the gasoline for explosives. If I read this correctly, the "two Asian men" had been picking up the gas to run generators, so their electrical energy usage wouldn't raise flags with the authorities. They were using it to run a very large marijuana-growing operation.
It was a case of gas for grass, and no skin off anybody innocent's a$$. But I guess they did get to ride for free... all the way to the police station.