A fire investigator says one of Utah's largest wildfires was caused by arcing between two sets of power transmission lines that were built too closely together and sent a powerful surge to the ground that ignited dry grass.

The Wood Hollow fire in June destroyed 160 structures, including 52 homes, killing one man.

Deputy Utah Fire Marshal Troy Mills says the fire began beneath two sets of high-voltage power lines. He says live wires either touched in high winds or swung close enough to spark. It scorched 75 square miles.

Rocky Mountain Power says a thief stripped protective cooper wire from its pole, but Mills says the surge would have overwhelmed the ground wire anyway.

Meanwhile, fires continue to burn across the West from California to Colorado, Oregon, Wyoming, Montana and Utah.