An Amtrak employee died from an injury suffered Tuesday morning at a rail yard in the South Loop, authorities said.

Another employee found the Martin Rivera, 42, about 7:15 a.m. on the tracks in the 1400 block of South Lumber, according to Chicago Police and the Cook County Medical Examiner’s Office.

Rivera was dead on the tracks when paramedics arrived, according to Chicago Fire Department spokesman Larry Merritt. He lived on the Northwest Side.

The employee was ”fatally injured” at an Amtrak mechanical facility in the vicinity of a service and inspection building, according to a statement from Amtrak spokesman Marc Magliari. No other injuries were reported.

An autopsy Wednesday did not rule on Rivera’s cause and manner of death pending further investigation, according to the medical examiner’s office.

The death was being investigated by the National Transportation Safety Board and the Federal Railroad Administration.