A wildfire that quickly went from modest to massive overwhelmed firefighters and frightened mountain towns in Northern California, but major efforts and a little luck had kept it from doing serious damage so far.

Bright orange flames burning in the hills were visible from the edge of town in San Andreas, a community of 2,700 people who were all told to evacuate briefly Friday before the fire moved in a favorable direction and they were told they could stay put, for now.

Hundreds of people from smaller surrounding communities had evacuated their homes and were filling up evacuation centers, one of which had to be moved twice Friday to get a safe distance from the flames.

The fire that had burned only about one square mile two days before had grown to more than 100 square miles and was just 5 percent contained, state fire officials said. Six homes were destroyed, and about 6,000 structures were under threat.

Firefighters chipped away at the huge blaze as they attempted to build fire lines. One of them said its growth was overwhelming.

"We feel so small in a big ocean right now," said Matt Sisneros, a bulldozer operator for the California Department of Forestry and Fire Protection. "We've been pushing dirt for about 18 hours."

Those in San Andreas, a gold-rush town about 60 miles southeast of Sacramento, were told they may still have to clear out. Some had already left.

Fred Oshiro, 85, said he, his wife and his wife's sister loaded up the car and went to an evacuation center only to learn that it had been moved.

"We're trying to evacuate," Oshiro said. "We were going to stay in the house and watch the fire, but the sheriff said you better take a hike."

"If the house burns down we'll lose a lot," he added, saying he had only brought "the three of us, and some essentials."

The evacuation center that twice moved had begun at San Andreas Town Hall.

"I had to move a kitchen full of food, 217 beds, three huge air conditioners," said Gina Gonzales, a Red Cross volunteer organizing the evacuation center.

The center was then moved to the nearby Calaveras County fairgrounds, home of the jumping frog contest made famous in a story by Mark Twain. But officials then decided to make that a staging area for the battle against the blaze, and the evacuation center was moved to Valley Springs about 20 miles from its original location.

Despite the runaround, volunteers said there was no lack of volunteers to help or supplies donated.

"They put out a call for 30 to 40 pillows, and we got 400," said Debbie Calcote, a Red Cross organizer. "It's what communities do."

Gov. Jerry Brown declared a state of emergency for the blaze burning in both Calaveras and Amador counties, helping to free up funding and resources in the firefight.

More than 2,400 firefighters, 246 engines, eight air tankers and 17 helicopters were assigned to fight the fire, which began Tuesday.

"The plan is to try to get this thing out," state fire spokeswoman Nancy Longmore said. "It's going to take quite a bit of work. We're in for the long haul here."

The cause is under investigation.

Meanwhile another California wildfire threatened to sweep through an ancient grove of Giant Sequoia trees. The lightning-caused fire has charred 172 square miles and grew by nearly 40 square miles in the last week.

In a fight to save the trees, firefighters have been clearing lines with bulldozers around the Grant Grove and putting up sprinklers, said Andy Isolano, a spokesman for the Clovis Fire Department.

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