Butte Fire, Mountain Ranch, California, Sept. 11, 2015
A house burns as the Butte Fire rages through Mountain Ranch, California, Sept. 11, 2015. Reuters/Noah Berger

A relatively small but fast-moving wildfire in California's Sierra Nevada mountain range grew overnight, destroying homes and threatening about 6,000 residences, fire officials said Saturday. The so-called Butte Fire has destroyed 15 homes in rural Amador and Calaveras counties, where it covers an estimated 64,728 acres, California Department of Forestry and Fire Protection representative Lynn Tolmachoff said. She said the fire grew overnight after officials initially overestimated the area of the blaze on Friday.

Tolmachoff said she expects the tally of destroyed homes to grow as inspectors assess the damage Saturday. Residents in the area were required to evacuate Friday. "There are a lot of homes there, but they're spread pretty far and wide," she said.

About 3,300 firefighters are working to contain the fire, which erupted Wednesday and spread late Friday near the former gold-mining town of Jackson. Officials listed it as 10 percent contained Saturday morning.

Gov. Jerry Brown declared Friday a state of emergency for Amador and Calaveras counties.

Separately, authorities ordered the entire community of San Andreas of more than 2,700 people to evacuate Friday, but lifted the order when flames headed away from town.

Flames from a larger Sierra Nevada blaze, dubbed the Rough Fire, edged close to a famed grove of giant sequoia trees in Kings Canyon National Park Friday.

Ground crews mounted an all-out defense of Grant Grove, a stand of ancient redwoods that includes the General Grant tree, one of the largest and tallest of all giant sequoias, as flames crept within a mile of the area, said Paul Garnier, a representative of the fire command. Giant sequoias are naturally flame-resistant, and most of the area's trees show scars from past wildfires, although officials hoped to keep the latest blaze out of Grant Grove -- a premier park attraction, Garnier said.

More than 2,200 firefighters were on the front lines of the blaze.

Ranking as California's largest active fire, the Rough Fire has scorched more than 119,000 acres and forced evacuations of park staff and visitors from a large swath of Kings Canyon. Containment was listed at 29 percent, although hundreds of homes in the park's vicinity have been evacuated, Garnier said.

(Reporting by Katie Reilly; Additional reporting by Alex Dobuzinskis and Steve Gorman; Editing by Daniel Wallis)