ANGELS CAMP, California -- Thousands of people rushed to escape one massive wildfire charging across California's tinder-dry Sierra Nevada foothills and another out-of-control fire that broke out in Northern California, sending four firefighters to the hospital with burns.

The northern fire began in Lake County, 100 miles (160 kilometers) north of San Francisco, and grew to about 15 square miles (39 square kilometers) in just a few hours, the California Department of Forestry and Fire Protection said Saturday.

The blaze has since exploded to more than 101 square miles (262 square kilometers) amid triple-digit temperatures and land parched from several years of drought. A thick layer of smoke kept air tankers and helicopters from flying Saturday.

The fire forced the evacuation of two towns as well as residents along a 35-mile (56-kilometer) stretch of State Route 29.

The firefighters were airlifted to a hospital burn unit, where they were listed in stable condition, department spokesman Daniel Berlant said.

The fire so far has destroyed 86 homes, 51 outbuildings and was threatening about 6,400 more.

“I lost my business - it's all burned up - my shop, my house, 28 years of living,” said Joe Thomas, who lives near Mountain Ranch. “I got to start all over. It's depressing.”

A choking fog of smoke and ash turned California's grassy, tree-studded Gold Country an eerie white. Away from the burned-out cars and smoldering remains of homes, Annette Stout and other residents who fled rested at evacuation centers.

“I grabbed my cats, their carriers, important papers, my husband death's certificate and his ashes,” said Stout.

California Governor Jerry Brown declared a state of emergency and more than 3,850 firefighters were assigned to the blaze. Its cause is under investigation.

Meanwhile, new evacuation orders were issued Saturday for the largest wildfire in the state, threatening to sweep through an ancient grove of Giant Sequoia trees. The fire, sparked by lightning on July 31, has charred 201 square miles, (521 square kilometers) according to the latest fire map released by the U.S. Forest Service.

In a fight to save the trees, firefighters cleared brush around the Grant Grove and set prescribed burns to keep the flames from overrunning it. By Saturday, the threat lessened when it became clear the backfiring and monitoring efforts helped protect the treasured trees, the Fresno Bee reported.

The grove is named for the towering General Grant tree that stands 268 feet (82 meters) tall. There are dozens of Sequoia groves in the Sierra Nevada, and some trees are 3,000 years old. (AP)