Sarpy County Sheriff's officials have identified the 8-year-old boy and his 66-year-old grandmother who were killed in a Bellevue mobile home fire last month.

Sheriff's officials say Devin Nielsen and Sandra Nielsen died in the February 23 fire.

Authorities say DNA testing was used to positively identify the two.

Autopsy results show they died of smoke inhalation.

Family members had identified Devin and his grandmother shortly after the fire.

The Nebraska Fire Marshal has said the fire was caused by combustible material that came in contact with a space heater.

Three others escaped the fire and were transported to a hospital. They later were treated and released.