Investigators say hot debris from a car's catalytic converter caused a wildfire that burned more than 300 homes in Southern California last year.

A seven-month investigation has concluded that pieces of metal from the interior of a converter started the so-called Freeway Complex fire in Yorba Linda last November.

The conclusion came in a final cause report issued Monday by the state Department of Forestry and Fire Protection.

Capt. Fernando Herrera says investigators could not determine what vehicle the debris came from and it's unlikely they'll ever to find out.

The fire destroyed 314 homes and forced 40,000 people to evacuate in Los Angeles, Orange, Riverside and San Bernardino counties. No one was killed or injured.

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