An arm of the Simi Valley fire tore through Pico Canyon and Mentryville and threatened Stevenson Ranch. The fire was sparked by the Val Verde fire and has burned more than 98,000 acres.

A joint effort by firefighters from throughout California ensured that the fire did not damage any structures Tuesday afternoon.

"We have not lost any structures, nor do we intend to," said Los Angeles County fire inspector Roland Sprewell.

Firefighters saved Mentryville structures from the blaze, a feat that firefighters did not believe they could accomplish. Ventura County Fire Capt. Ed Spafford expressed his doubt as the fire rolled down a hill, minutes before it hit the edge of the state historical park.

"(Saving Mentryville) is going to be damn near impossible, but we're going to give it our best," Spafford said.

Two Ventura County hand crews struggled to move brush and light back fires to halt the progress of the Simi Valley fire toward Santa Clarita structures in Pico Canyon, nearly a mile west of Mentryville. Around 1 p.m., the fire jumped the narrow trail firefighters used to make a stand and the wind pushed the blaze out of control toward Mentryville and Stevenson Ranch.

Ryan Flitt was among the almost two dozen Ventura County hand crew members who evacuated to Mentryville after the back fire failed.

"Every ... time; all that work burned over," he said.

The firefighters prepared to save the structures in Mentryville as the flames raced down the hillside. Fire Capt. Roy Dull, who observed the firefighting efforts while off-duty, said the fire was the worst he had ever seen in the area.

"They've got this one dialed in," Dull said. "It's going to have to be a hard battle."

Firefighters hosed down the structures and set back fires throughout Mentryville, successfully keeping the fire at bay.

Areas of Stevenson Ranch were involuntarily and voluntarily evacuated. The area was closed off for hours as emergency crews worked to keep order and fight the fires that crept toward neighborhood areas. Concerned residents gathered in the streets to watch the fire approach.

"I'm just shocked. I can't believe it," said Susanne Ulloa, a Stevenson Ranch resident.

Red Cross centers were set up at College of the Canyons and Hart High School.

Henry Mayo Newhall Memorial Hospital put a fire disaster plan into place Tuesday afternoon. The hospital increased its emergency room staff and provided breathing masks to those who needed them.

The fire was not under control Tuesday night, though firefighters were successful in setting back fires, Sprewell said.

"Right now, we're just observing the fire's behavior and allowing the fire to burn out fuel," he said.