A swiftly spreading wildfire destroyed hundreds of homes and forced thousands of residents to flee as it roared unchecked through the Northern California community of Middletown and nearby neighborhoods, fire officials said on Sunday.

The so-called Valley Fire, now ranked as the most destructive among scores of blazes that have ravaged the drought-stricken Western United States this summer, came amid what California fire officials described as "unheard of fire behavior" this season.

The California Department of Forestry and Fire Protection put the total number of Valley Fire evacuees on Sunday night at around 19,300.