The worker killed at a worksite off Jeff Road in Huntsville was unable to escape the collapsing dirt of the sidewall of a trench that collapsed.
The cause of death is traumatic asphyxiation as the result of compression from the substantial weight of the sidewall, said Madison County Coroner Dr. Tyler Berryhill.
Berryhill said the invesigation is ongoing.
The identity of the victim has not been released.
Don Webster, Huntsville Emergency Medical Services spokesman, said authorities responded to the site on the 400 block of Jeff Road.
Fire Marshal Dan Wilkerson said it was a trench collapse, and that there is one victim.