Maui firefighers are investigating as arson the cause of a fire that caused $15,000 damage Sunday to a single-story wooden structure that was under construction in Waihee.

Firefighters arrived at 9:32 a.m. Sunday but could not make access down the narrow dirt road leading to the house, 2594 Kahekili Highway. Firefighters left the fire truck on the highway and had to walk in about 400 yards.

Crews found a section of the 1,800-square-foot house had caught fire and nearly burned itself out. Firefighters used the house’s garden hose and a portable water extinguisher to douse the smoldering fire.

The house had not yet been occupied.