The break came after suspect James Lee DiMaggio's blue Nissan Versa was found in central Idaho about 8 a.m., San Diego County Sheriff Bill Gore said. Federal, state and local authorities were scouring the Frank Church-River of No Return Wilderness in Valley County, where the vehicle was found.
A group of horseback riders told local authorities that they had spoken to two people believed to be DiMaggio, 40, and his alleged captive, Hannah Anderson, 16. The riders came across the pair Wednesday morning but said it wasn't until they returned later that day that they realized the girl may have been Anderson.
The witnesses said the man and girl had a tent and backpacks but looked out of place in the rugged terrain because they had light camping equipment, Gore said.
The witnesses said the girl appeared to be well, he added.
"I'm very confident and I think we should all be optimistic that she appeared to be in somewhat good health and alive on Wednesday," Gore said.
Authorities found the car Friday "just off a road," covered in brush, Gore said. Its license plates had been removed, but it was identified by its vehicle identification number, he said.
Authorities planned to use bomb and arson technicians to search the vehicle to ensure it was safe, he said. Earlier this week, sheriff's officials warned that the car might be rigged with explosives.
The brush "was an attempt to hide it, to keep it out of plain view," he said.
"We've got to assume he is armed, and that is the word we've put out to everybody," Gore said.
Locals said the area is difficult to navigate, especially for people unfamiliar with it.
Cheryl Bransford, 62, who works as a wilderness guide out of Ya-Hoo Corrals at Payette Lake, north of Cascade, described the terrain as very steep, with areas of "almost jungle-like" vegetation.
The River of No Return Wilderness includes more than 2 million acres of federally designated land, marked by rivers, canyons and mountains.
Upon receiving the Amber Alert on Friday morning, Bransford said she and other outfitters started locking unused vehicles, something they don't usually do.
She also took another precaution.
"I keep a .357 within minutes away — loaded," she said.
The case began Sunday after the body of Hannah’s mother, Christina Anderson, was found in the garage at DiMaggio’s burning San Diego County home. The body of a boy — now confirmed to be that of Hannah’s 8-year-old brother, Ethan — was found in the home.
Anderson died of blunt force trauma and may have been hit with a crowbar, a source close to the investigation told The Times. An arrest warrant has been issued for DiMaggio, San Diego County sheriff's officials said.
DiMaggio has been described as a close friend of the Anderson family — the children called him "Uncle Jim," authorities said — but authorities were still trying to sort out his relationship with Hannah.
Some of her friends have told the media that DiMaggio had a crush on the teen.
It remains unclear whether Hannah was abducted or went with DiMaggio willingly, Gore said.
The case began to receive national attention as the search for the pair widened. An Amber Alert, originally issued in California, was later broadened to Oregon, Washington and Nevada. Idaho was included Friday morning.
The FBI is also involved, along with authorities in Mexico. DiMaggio's home is a few miles north of the border.
Brett Anderson, Hannah's father, told the Associated Press on Friday that he was "very happy" that Hannah was apparently spotted alive. He said he couldn't explain why the girl didn't ask the horseback riders for help.
"We don't know what kind of frame of mind she was in or what he told her," Anderson said. "Maybe if she acted differently, there would be more dead people."
Mather reported from Boise, Branson-Potts and Wells from Los Angeles.