A fire that killed a 33-year-old mother and her 9-month-old daughter last week in Kaimuki was caused by leaked propane vapor, the Honolulu Fire Department said Sunday.

HFD Capt. Scot Seguirant said the propane vapor was ignited by an electrical water heater. He said fire investigators have concluded their investigation and determined the cause of the fire was accidental.

The blaze started at about 8:10 a.m. Wednesday at 733 A Laukaha St. and arriving firefighters found the woman’s body in the garage and the baby in the living room.

The victims were identified as Connie Moribe Wharton and her daughter Sophia, the wife and daughter of Honolulu Police Lt. Nathan Wharton, who was not home at the time.

Firefighters estimated the fire caused about $720,000 in damage.

Friends of the family have organized a celebration of life for Connie Wharton and her daughter from 4 to 10 p.m. Nov. 4 at Artistry Honolulu in Kakaako. Organizers said the funds will go to Nathan Wharton for funeral and other expenses.