A natural gas wall heater is believed to have caused a residential fire that killed a woman and her two elementary-age children in north Alabama, officials said.

The blaze, which occurred early Monday in the Winston County town of Haleyville, was not suspicious, Alabama Fire Marshal’s spokesperson Jennifer Bowen told al.com.

Cara Evans, 44, and her two children, 8-year-old Annabelle and 4-year-old Jacob, died in the blaze, officials said.

The children were students at Haleyville Elementary School, and officials with the system have established a fund to help with funeral expenses and to assist the children’s father, who Bowen said an investigator determined was at work when the fire began.

Bowen said a neighbor reported the fire about 3:30 a.m. Monday, when temperatures were in the 20s in the area and snow was falling across parts of north Alabama.