Thursday's fire that destroyed the Niu Valley home of Polynesian voyaging navigator Nainoa Thompson and his wife, KHON-TV reporter Kathy Muneno, was caused by a malfunction of an electric tankless water heater, a fire department spokesman said yesterday.

Capt. Earle Kealoha said the fire originated in a crawl space under the house at 440 Puamamane St.

Damage was estimated at $300,000 to the home and $50,000 to its contents.

No one was injured in the fire. The damaged house is one of five structures — four of them homes — on a five-acre Thompson family compound at the end of Puamamane Street.

Tankless water heaters heat water very quickly, and only when a person turns on the hot water. Such "on demand" water heaters do not store hot water in a tank and are generally more efficient, and cheaper to operate, than traditional storage-tank water heaters, according to the U.S. Department of Energy.

The single-story house that burned is near the entrance to the Thompson property. The fire was reported at 4:12 p.m. and reported under control at 4:30 p.m.

Thompson is executive director of the Polynesian Voyaging Society. Since 1980, he has led trans-Pacific canoe voyages using traditional, noninstrument navigation. He also serves as vice chairman of the Kamehameha Schools board of trustees.