Firefighters cannot determine what sparked a $20,000 shed fire Wednesday in Waimanalo.

About 20 Honolulu firefighters from three companies were sent to the fire on a private road off Kumuhau Street at 8:40 a.m. Wednesday and had to stretch about 1,500 feet of hose to carry water from a fire hydrant on Kumuhau Street, said fire Capt. Terry Seelig. Despite the distance to the hydrant, firefighters brought the flames under control in about 15 minutes. Seelig said a fire investigator determined the fire  appeared to be electrical in nature, but the investigator could not determine the exact cause.

The blaze destroyed about $5,000 worth of tools in the shed and melted the structure’s aluminum walls and caused $15,000 structural damage. No one was hurt.