Police reports state that the thieves greased the train track beforehand, causing the 54-wagon vehicle to slow down due to uneasy controls. The criminals then proceeded to use a tow truck to remove the containers of corn.
The a-maizing highjacking went smooth as silk, so it is believed the kernel of truth is that the thieves stalked the train ahead of time. Link -via Arbroath, whose commenters provided the puns.