The fires have swept through more than 39,000 acres so far. Officials report that at least 16 people have died.

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.

The Lidia fire, which has burned around 395 acres, has been fully contained as of Saturday morning, according to CAL Fire.