PARADISE, Calif. (AP) — California’s largest wildfire so far this year is flaring up, but authorities say it's because flames are chewing through unburned islands of vegetation within a perimeter that firefighters have built.

It produced a huge fire cloud Thursday, which is a towering column of smoke and ash that can pose a danger to firefighters.

The Dixie Fire in the mountains of Northern California has destroyed more than 40 homes and other buildings and threatened over 10,000 on Friday.

In southern Oregon, the nation’s largest wildfire also is burning interior pockets of vegetation.

The U.S. Drought Monitor says critically dry conditions persist across Northern California and the Northwest, where there has been an expansion of exceptional drought.