Investigators on Thursday continued the grim task of trying to determine what caused a fire that killed four children at a Conyers duplex. An investigator said it could be days before they have an answer as to how the fire started.

Officials said the children’s mother, Reba Glass, who survived, could be the key to providing an answer, but she was still in shock.

Thursday morning, a makeshift memorial of stuffed animals stood in the parking lot behind the duplex where tragedy struck late Tuesday night.

Shameka Swift brought a stuffed bear to add to the memorial Thursday morning.

Swift, who said she’d known Glass since middle school, said “There’s nothing you can say and nothing you can do to make it feel better, but bringing [the bear] was just reaching out to let her know we’re her and we support her.”

Only one child survived the blaze. Darnell Glass, who will turn 6 Saturday, still didn’t know Wednesday afternoon that his three brothers and older sister were dead.

Darnell’s mother, Reba Glass, learned the devastating news early Wednesday morning at Grady Memorial Hospital, where she is being treated for severe burns over 40 percent of her body.

“She sat up in bed and started screaming for her kids,” said Chante Hullum, Glass’ cousin.

Before learning the truth, Glass believed her children had made it out alive, Hullum said. Darnell, who was not badly injured, was treated and released at Children’s Healthcare at Egleston.

The source of the fire remains unknown, and Rockdale County Fire and Rescue Chief Daniel Morgan said it could be days before investigators have an answer. Due to the intensity of the blaze, they didn’t know Wednesday whether the duplex was equipped with smoke detectors.

“This is just a bad day,” Morgan said.

The fire started around 11 p.m. at 1149 Pinedale Circle, where the family had lived since November. They were scheduled to move out Wednesday.

Police said Glass was asleep in one of two upstairs bedrooms with her two youngest children, 3-year-old Armoni and 7-month-old Deon. Evidence shows that the fire started in the second story bathroom or hallway, investigators said.

Darnell, whom the family had nicknamed “Fat,” told officers that his mother saved him by throwing him out a window.

A neighbor, Rockdale County High School junior Lamonta Stroud, said he returned home a short time later to hear Glass screaming: “My babies, my babies!” She had made it out of the home with her mother, Rosetta Mitchell, but four children remained inside.

Stroud attempted to get upstairs, but his older brother pulled him back. Stroud — hailed for his efforts by Conyers police — said he ran to the back of the house, where he heard someone banging on the second-story window. He said he spotted 9-year-old Adaria, but then she disappeared.

“I was telling them to come to the back, come to the back, but nobody came,” he said.

By then police had arrived. Sgt. Bill Connell, the first officer on the scene, headed up the stairs, fire extinguisher in hand.

“I could feel (the fire) burning the top of my head,” Connell said. “There was nothing that wasn’t burning.”

Stroud said that by then the back bedroom, too, was all ablaze.

“The flames were everywhere, four to five feet tall,” he said. “I couldn’t see much, just smoke.”

That was the scene when Rockdale County Fire and Rescue arrived minutes later.

“They had flames coming out at least two windows, one on the back side,” Morgan said. “They entered the home, went upstairs and extinguished the fire while another crew retrieved the children and brought them out to try to revive them.”

Deon, Armoni, Adaria and 7-year-old Dashawn were pronounced dead at the scene.

Relatives said Darnell is in the care of his father, also named Darnell Glass. He and Reba Glass are separated, they said, and he is not the father of the two youngest children.

Conyers Police Chief Gene Wilson said investigators are still trying to piece together exactly what happened. They have spoken with Mitchell, the children’s grandmother, and will talk with Reba Glass when she’s able.

“Right now, what we think happened is the fire started upstairs, the mother was able to throw one child out the window, then got the grandmother who was sleeping downstairs out of the house,” Wilson said.

“The mother is probably going to be the key” in creating a more complete picture, he said.

Relatives say Glass is still in shock. “She’s kind of in and out. One moment she’s calm and then crying,” said Glass’ sister-in-law, Santana Baker. “She has lots of burns, on her back, forehead, the inside of her hands, her arms and legs.”

“All she’s saying is, ‘My babies. My babies. My babies are gone.’”

Adaria loved to dance and was known for her hugs, Baker said. Dashawn, was laid back.

Little brother Amoni “kept everything alive,” said Baker, who also lives in Conyers. “He was the little big brother” to the baby, Deon, who was born three months premature.

The family is still trying to figure out how to break the news to Darnell, who loved playing basketball, football and video games with his brothers.

“That’s something we haven’t sat down and talked about,” Hullum said. “I know it’s going to be difficult to tell him what happened to his brothers and sister. Hopefully we can break it down in some way he can understand.”

A community prayer service has been scheduled for Thursday at 7:30 p.m. at Macedonia Baptist Church, 1052 Barton Street in Conyers.

A Conyers funeral home, Levett & Sons, has offered to handle the funerals at no cost, county officials said. A memorial service for the children will be held Jan. 19 at 11 a.m. at Macedonia Baptist Church.

A Glass Family Memorial Fund has been set up with Wells Fargo.