REDDING, Calif. (AP/CBS13) — Crews on Sunday were continuing to battle the three largest fires burning in Northern California.

The greatest threat came from the Salt Fire, which broke out Wednesday near a highway and destroyed 41 buildings, including 27 homes, in a rural area north of Redding. As of Sunday morning, it had grown to burn more than 9,100 acres and was 15% contained.

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Authorities suspect the fire started from a hot piece of metal that flew off a car or truck on Interstate 5. They haven’t found the vehicle.

Some residents were allowed to return home Saturday but evacuation orders and warnings remain in place for several rural communities, Shasta-Trinity National Forest officials said.

The area could see triple-digit temperatures on Sunday.

Fire officials said hot weather and parched brush made perfect conditions for the kinds of disasters that have destroyed thousands of square miles of land in recent years, mainly in rural and forest areas.

The state’s largest blaze, the Lava Fire burning partly on the flanks of Mount Shasta, was 39% contained Sunday after burning more than 24,700 acres as of the afternoon. The blaze, sparked by a lightning strike on June 25, forced several thousand people from their homes, but most of them were allowed to return late Thursday.

Still, officials at a community meeting Saturday acknowledged the frustration and asked for patience, saying they don’t want to let people back in and have flames spread quickly.

“The concern is repopulating too soon and having this be aggressive,” Siskiyou County Sheriff Jeremiah LaRue said.

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To the northeast, the Tennant Fire in the Klamath National Forest, has burned five buildings, including two homes, and threatened several hundred more. It grew slightly overnight to burn more than 10,400 acres. But officials reported progress and the fire was 29% contained early Sunday.

Mop-up began on the western flank while flames remained active on the east side, where evacuation orders and warnings are still in place.

The trio of blazes were among more than a dozen wildfires that erupted in recent days in the midst of hot, dry conditions usually seen in August, fire officials said.

See photos from the three fires below.

In Southern California, evacuations were ordered after a wildfire broke out and grew rapidly Sunday near an off-road vehicle park in Gorman, about an hour northwest of downtown Los Angeles.

National parks put out renewed calls for people to heed restrictions on campfires and other fire risks during the holiday weekend.

Klamath National Forest officials said below-average winter rainfall and recent record-high temperatures “mean that one single spark can start a wildfire.” Visitors were warned not to drive or park on dry grass or brush because hot exhaust pipes and mufflers could torch them.

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Last year, California wildfires scorched more than 6,562 square miles (17,000 square kilometers) of land, the most in its recorded