Sequoia fire believed accidentally started

Suspect to be arraigned Friday

A water-dropping helicopter flies past a wall of flame in the Giant Sequoia National Monument.

KERNVILLE, California (CNN) -- The woman arrested on suspicion of setting a fire in the Sequoia National Forest probably did it accidentally, forest service officials said Thursday.

"It is believed an escaped campfire caused the fire, but [we] do not believe it was intentional," a U.S. Forest Service spokeswoman told CNN.

Peri Van Brunt, a Kern County resident, was apprehended Wednesday, forest service officials said. Her arraignment is scheduled for Friday morning in a Fresno federal district court, a court clerk said.

Even if the fire was not set intentionally, federal law applies because it was started without a permit in a national forest, officials said.

Van Brunt is being held in a detention facility north of Bakersfield, according to a Fresno newspaper.

The fire, dubbed the McNalley blaze, is in its fifth day, with more than 1,500 firefighters on the front lines about 50 miles northeast of Bakersfield.

CNN NewsPass VIDEO Firefighters struggle to stop the McNalley wildfire, as authorities arrest a woman suspected of starting it. CNN's James Hattori reports (July 25) Play video

More than 55,000 acres have been consumed by the fire and it remains only 5 percent contained, a Forest Service spokesman said.

Firefighters have been somewhat encouraged because they have been able so far to prevent major damage to nearby towns and cabins, but they remain concerned, a fire official said.

"It's not too much of a stretch of the imagination for this fire to double in size before we actually have any opportunity to corral it," he said.

The proximity of the blaze to several groves of ancient Sequoia trees has also raised concerns, with flames approaching as close as a mile or two at times, fire officials said.

The most threatened group of the thousand-year-old sequoias are those within the Giant Sequoia National Monument, created approximately two years ago by President Clinton to extend protection to trees outside Sequoia National Park.

Most of the trees inside the park are about 40 miles away and remain unthreatened.

Sequoia bark is naturally fire-resistant, and the trees' high, widely spaced branches reduce the chance of flames engulfing the entire crown. But human efforts to prevent fires have allowed trees around the tall sequoias to grow higher and allowed litter to build up on the forest floor, leading to hotter, higher fires, experts say.

The lack of periodic, lower-temperature fires also have inhibited sequoias' ability to reproduce -- sequoia cones release their seeds only when heated by fire.

One thousand people in southern California have been evacuated because of the fire, including 400 Boy Scouts who had to abandon camp when the blaze broke out Sunday.

All told, some 34 large wildfires -- each 500 acres or more -- are burning this week in nine states: Alaska, Washington, Oregon, California, Colorado, Wyoming, Idaho, Utah and Montana.

About 3.8 million acres have burned since the beginning of the year -- more than twice the number of acres than the average for the same period in the last 10 years.