Police say the incident happened at 11:36 a.m. Tuesday on the railroad tracks near Banning Park.
Delaware State troopers and Amtrak Police officers converged on the scene at Park Lane then walked north along the tracks.
The victim's body was located behind an industrial site near the end of Robinson Lane.
Investigators say person was hit by the Amtrak Acela Express, travelling from Boston to Washington, D.C.
Images from Chopper 6 HD showed an Amtrak Acela train stopped some distance past the accident scene.
There were 150 people on board the train at the time of the crash. They were transferred to another train to continue their trip.
Investigators say the authorized track speed in that area is 110 MPH, but it is not known if the train was going that fast at the time of impact.
There were some minor delays to other trains as a result of this incident and the investigation.