CONYERS, Ga. (AP) — A 6-year-old boy playing with a lighter started a blaze in Georgia that killed four of his siblings and left his mother badly burned, authorities said Friday.

A fire Tuesday night tore through a duplex in Conyers — east of Atlanta — killing 8-month-old Deon Glass, 3-year-old Armoni Roberts, 7-year-old Dar'Shawn Glass and 9-year-old Ah'Dariya Glass. The unidentified 6-year-old boy was thrown from a second-story window to safety and survived the blaze, as did the children's unidentified grandmother. Rockdale County fire and rescue officials said the boy was taken to Children's Healthcare of Atlanta at Egleston for non-life threatening injuries.

Reeba Glass, the children's mother, was hospitalized in serious condition with burns throughout her body at Grady Memorial Hospital, officials said.

Interviews and an examination of evidence led investigators to determine that the boy set the fire, said Daniel Morgan, Rockdale County's fire and rescue chief. Investigators said no accelerants were found inside the house and all other accidental causes have been ruled out.

The home's two bedrooms were located on the second floor, and investigators say the fire started near a second-floor bathroom and hallway. There was one smoke detector in the house, but fire officials have said there were no batteries in it at the time of the blaze.

Associates at a local funeral home are arranging free services for the four children who died in the fire, but representatives say the date depends on when the children's mother is discharged from the hospital.

A pastor at Macedonia Baptist Church in Conyers is working to collect donated household and clothing items to offer the survivors, and Morgan said officials are working to ensure the 6-year-old boy receives counseling from the division of family services.