Kaegan Anthony Roberts died in the April 5 fire in southeastern McMinn County.
Keith Anthony Roberts, 25, told investigators his son was sleeping when he took his girlfriend to work. Roberts said he was gone about 30 minutes and returned to find the house burning.
A Sheriff's Department statement said the residence was ``fully involved'' when volunteer firefighters arrived about 6 a.m.
Records show the boy's father and emergency workers made unsuccessful attempts to resuscitate the boy.
Investigator Tim Carver said Thursday the cause of the fire was not determined.
Bob Pollard, assistant director for bomb and arson in the state fire marshal's office, previously said the ``fire was accidental'' and an autopsy showed the child died from smoke inhalation.
Roberts was charged with felony child neglect and criminally negligent homicide before the grand jury returned the indictment Aug. 17. He remains free on a $25,000 bond, pending a Nov. 29 court hearing.
