The cause of Thursday’s residential fire in Makiki where two people were found dead was an unattended portable cooking burner, the Honolulu Fire Department said.

The origin of the fire was the exterior porch in a makeshift cooking area. The fire was classified as accidental, the fire department said.

Nearly 40 firefighters responded to the structure fire at 962 Spencer St., Unit B just before 12:50 p.m. Thursday. When they arrived, the home was engulfed in flames.

Fire crews battled the fire and found a 77-year-old man dead just outside the home under the exterior staircase of the residence and a 76-year-old woman in a bedroom on the ground floor, according to the fire department.

Firefighters brought the blaze under control by 1:04 p.m. and extinguished it at 1:40 p.m.

Damage to the structure and contents was estimated at $539,000 and $4,000 to other losses.

The fire department noted there were no smoke alarms in the residence.

The Honolulu Medical Examiner’s Office has yet to release the names of the man and woman.