Updated

An electrical line in a tree sparked a devastating summer wildfire in central California that killed an elderly couple and destroyed hundreds of homes, investigators said Thursday.

Insulation from the electrical line rubbed the tree and wore down over time, dropping hot, molten material into the dry grass below that sparked the fire, officials said.

The fire raced up a Lake Isabella hillside prone to burning, said Kern County Fire Chief Brian Marshall. But this year, firefighters couldn't stop the flames, which eventually scorched 75 square miles and turning 280 homes into tangled rubble.

"This is one for the record books," Marshall said. "It's not anything we ever want to occur again."

The fire sparked in late June in the community of Lake Isabella, an hour's drive east of Bakersfield in the southern Sierra Nevada.

The conditions were ripe for a fire, said Marshall, noting that five years of drought had dried out the mountainous landscape covered by grass and dead trees. Wind and hot weather drove the flames, he said.

An elderly couple trying to flee from the flames were overcome with smoke outside of the house and killed. In other neighborhoods, mobile homes residents raced to safety through thick smoke and roaring flames.

"Everything they had was destroyed," Marshall said. "They literally escaped with the clothes on the backs."

Fighting the fire cost $23 million, a figure that Marshall said doesn't account for the property lost by hundreds of residents, some still homeless.

Federal officials will provide new homes for 27 residents in a rebuilding process that Marshall said will take time, officials said. Several agencies collaborated on the investigation pinpointing the fire's cause, officials said.

Gabe Garcia, a spokesman for the U.S. Bureau of Land Management, said his agency will next determine who is responsible and if criminal charges should be filed.

The fire started on private property, and officials did not name the owner. Garcia said that determining the next steps in the investigation could take weeks or longer.