Fire investigators said spontaneous combustion of discarded sanding dust caused a three-alarm fire at a Manoa residence late Wednesday.

Fourteen units with firefighters responded to the fire at a two-story, multi-family home at 3557 Kumukoa Street at approximately 9:35 p.m.

Honolulu Fire Spokesman Capt. Scot Seguirant said the residence was unoccupied at the time of the fire.

When firefighters arrived, they observed smoke and flames throughout the second floor. Firefighters brought the fire under control at about 10:30 p.m. and extinguished it just before 10:50 p.m.

Seguirant said the second floor of the home was reportedly undergoing renovation work.

No injuries were reported.

Damage was estimated at $829,000 to the structure and $12,000 to its contents.