HOUSTON—Investigators on Wednesday said the mother of two 18-month-old twins killed in a Houston duplex fire was not home when the blaze started.

Firefighters were called to the scene in the 1700 block of Sam Wilson in northeast Houston around 12:30 a.m.

Neighbor Alfred Goodman said he called 911 after he was awoken by the frantic mother.

“I unlocked my door and went back there, and I seen all this fire shooting out the front door. You know, we couldn’t do nothing,” neighbor Alfred Goodman said. “I was the first one back there, me and a neighbor from upstairs. But we couldn’t do nothing … It was too late.”

The mother was there when the firefighters arrived, screaming for help and saying that her little girls were trapped inside.

Firefighters were able to get the blaze under control, but it was too late for the children.

The flames seemed to have spread quickly through the home, engulfing the couch where the girls slept.

Arson investigators removed a gas stove from the home. 

They said it may have been the source of the fire.

The mother told police she had turned on two burners and left the home for a short period of time overnight while the girls were sleeping.

A woman who described herself as the mother’s best friend said the girls’ deaths were a tragedy.

“They was sweet. They were something that I never could have. She don’t deserve this, her husband or her kids,” the woman said through tears.

Investigators said they’re awaiting an autopsy to confirm the identity of the twins and their exact cause of death.

Police released the mother after she was questioned, and she hasn’t been charged with a crime.