(Louisiana, Mo)--An investigator says a Thursday morning fire that killed a three-year-old Louisiana boy was accidental.

Missouri Division of Fire Safety spokesman Mike O’Connell said Friday that a specific cause had not been determined, but that neither an electrical problem nor smoking materials could be ruled out. There were no signs of arson, authorities said.

The victim was identified as Riley Jeffrey Rieser. Pike County Coroner Jim Turner said an autopsy was done in St. Louis County, but that he had not gotten results by Friday afternoon.

O’Connell said the fire started in a living room at the back of the house, where the boy’s body was found. The two-story wood frame home is at 405 S. Main across from MFA Agri Services in a neighborhood of older homes south of the downtown area, just a couple of blocks from the Mississippi River.

The boy’s parents, whom authorities identified as Ryan and Catherine Miller, fell asleep watching television while the child slept in a bedroom.

The couple was awakened by the smoke.  Both escaped through a rear door, but had injuries. They were taken to the burn unit of Springfield, Ill., Memorial Medical Center by family members and released Thursday night.

City Administrator Bob Jenne said one firefighter in full gear tried to make entry and had to back out because of the heat.

Jenne said Louisiana police used an electroshock weapon on Ryan Miller to prevent him from returning to the burning home to retrieve the child. He said the police took the action for safety reasons.

Crews were called at 12:58 a.m. Thursday and arrived within five minutes. About 25 firefighters from Louisiana, Buffalo Township, Spring Creek and Pleasant Hill, Ill., responded.

Louisiana Fire Chief Mike Lesley said flames burned through the first floor ceiling and got into the second floor. The fire was brought under control in about an hour, he estimated. Some firefighters were on the scene until 10 a.m. Thursday.

The last fatal fire in Louisiana was on Aug. 4, 2011, when a man died in an accidental electrical blaze at his North Third Street home.

A makeshift memorial of flowers, stuffed animals and balloons had been set up Friday in front of the Miller home, where the smell of burnt wood hung in the air more than 36 hours after the fire was reported.

Funeral arrangements were pending.

(Story contributed by journalist Brent Engel)