Northern California Wildfire Reduces Streets to Smoldering Rubble, Destroys Over 175 Structures

— -- Entire streets have been reduced to smoldering rubble, and more than 175 buildings and other structures have been destroyed, as a Northern California wildfire continues to spread.

The fire about 100 miles north of San Francisco has so far spread to 4,000 acres and is 5 percent contained, officials said.

The blaze on Sunday swept into Lower Lake, a town of about 1,200 people, according to The Associated Press, where it burned buildings including a post office, a Habitat for Humanity office and a winery.

Thousands of people have been evacuated since the fire began Saturday, according to the Associated Press. The cause is under investigation.

ABC News' Mary Bruce contributed to this report.