ROCKY MOUNT, EDGECOMBE COUNTY -

Investigators have determined the cause of a house fire that killed a 4-year-old boy and his 63-year-old great-grandfather in Rocky Mount.

The fire at 1713 Springfield Rd. Monday night was accidental, and started when a portable generator was being fueled on the back porch. The gasoline vapors were  ignited by an undetermined heat source, according to a spokesperson with the City of Rocky Mount.

Killed in the fire were 4-year-old Isaiah Chase and his great-grandfather, 63-year-old Frederick Fasegha, said the man's wife.

When crews arrived at the single-story home, it was fully engulfed in flames, officials said. The home is considered a total loss.

No one else was inside the home when the fire happened.

Officials said storms Monday night caused power outages in the area.