Fire investigators said spontaneous combustion of sanding dust caused a fire Wednesday morning at a Manoa residence.

It took 14 Honolulu Fire Department units staffed with 53 personnel to extinguish the fire at a two-story home on Kumukoa Street.

The structure’s second- story was under renovation at the time of the fire, and both the upstairs and downstairs were unoccupied.

Investigators said the fire started accidentally when sanding dust from a flammable finish discarded into a plastic bag spontaneously combusted.

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

No injuries were reported.