The truckie discovered the body of a young male in a drain beside the south-bound lane, just south of the Gasoline Alley service station, about 9.30am.
Ewers said an initial survey of the scene indicates that the young man may have been riding a bicycle southbound on SH1.
The Police Serious Crash Unit was surveying the scene while the Police Commercial Vehicle Investigation Unit was examining the truck.
Both lanes of SH1 were open but traffic would be slowed through the scene while investigations continued.
A Northern Advocate reporter at the scene said kaumatua had arrived to bless the scene.