In the case of the Eaton Fire, the investigators are likely to use magnets to help them hunt for the tiny, melted pieces of metal that could have been shed by power lines if they slapped together. But the existence of the metal doesn’t necessarily indicate that’s how the fire started, Nordskog said.

Firefighters are hoping for a break Friday from the fierce winds that have fueled massive blazes in the Los Angeles area, killing 10 people, obliterating whole neighborhoods and setting the nation’s second-largest city on edge.