- NEW: "They both appeared to be in good health," sheriff says of suspect and girl
- NEW: Horseback riders see man matching Amber Alert suspect's description
- NEW: Bomb technicians are examining suspect's car for possible explosives
- NEW: Suspect's vehicle was hidden by brush outside Cascade, Idaho
(CNN) -- The national manhunt for California Amber Alert suspect James DiMaggio and his alleged 16-year-old captive girl has moved to the Idaho wilderness after horseback riders saw a man and a girl fitting their description, authorities said Friday.
Investigators subsequently found DiMaggio's car hidden by brush, with its license plates removed, San Diego County Sheriff Bill Gore told reporters. Authorities confirmed the car's ownership by its vehicle identification number, he said.
The vehicle was located in the remote River of No Return Wilderness area in Cascade, Idaho, Ada County sheriff's spokeswoman Andrea Dearden said.
Not aware of the manhunt at the time, the campers and hikers on horseback saw the man and girl Wednesday, but they called police after they saw news account that evening, police said.
"It is a wilderness and extremely difficult terrain to navigate," Gore said.
The vehicle will be examined by bomb and arson technicians to ensure it's not rigged with explosives, Gore added.
The horseback riders observed the woman -- believed to be 16-year-old Hannah Anderson, whom DiMaggio, 40, has allegedly kidnapped -- to be in good condition, Gore said.
"They both appeared to be in good health," Gore said.
The man and woman sighted by the campers were carrying backpacks, with a tent, about six miles outside Cascade, Idaho, Gore said.
Meanwhile, authorities continued Friday to deem DiMaggio a dangerous suspect because he is accused of killing the girl's mother and possibly the woman's son.
A search of the burned-down house belonging to DiMaggio has led law enforcement to this conclusion: "We don't hold anything past this person," as one official put it.
Authorities found the body of Hannah Anderson's mother, Christina, in DiMaggio's San Diego-area home, and a second body likely to be Christina Anderson's 8-year-old son, Ethan.
Details of what investigators have uncovered at the scene remain under wraps, but it has led authorities to warn that the suspect's car may be rigged with explosives.
"We have a heightened concern that's based on the evidence we have been collecting at the scene all week long," San Diego Sheriff's Department Capt. Duncan Fraser told CNN Friday.
Sightings of suspected kidnapper's car 
Searching for Hannah and Ethan 
Witnesses saw a man grab 9-year-old Michaela Joy Garecht outside a store near her home near Oakland, California, in November 1988. Here, Michaela is seen in a childhood photo next to an image of what she might look like today. If you have seen Michaela or any of the faces in this gallery, please contact your local FBI office or call 1-800-THE-LOST. 
The discovery of the three young women missing for a decade in Cleveland immediately raised hopes for Ashley Summers, who went missing in July 2007 at age 14 within blocks of the other three. Here, she is shown next to an age-progressed rendering of her on the right. 
Christina Adkins was last seen in Cleveland in January 1995. She was 18 years old and five months pregnant when she disappeared. 
Jessica Heeringa, 25, was abducted in April from an Exxon station in Norton Shores, Michigan, where she was working alone, sometime around 11 p.m., police said. Police have released a sketch of the suspect, described as a white male, about 6 feet tall, between 30 and 40 years old, with wavy hair parted in the middle. 
Madeleine McCann was a few days shy of her 4th birthday when she disappeared during a 2007 family vacation in Portugal. Despite a huge police investigation and massive media coverage, she remains missing. 
Haleigh Cummings, 5, was reported missing from her family's home in Satsuma, Florida, in February 2009. The National Center for Missing & Exploited Children released the age-progressed photo to show what she might look like at age 8. 
Eighteen-month-old Amir Jennings was last seen with his mother in Columbia, South Carolina, in November 2011. Both were reported missing by a family member in early December 2011. Amir's mother was located a few weeks later after she was involved in a car accident. Amir was not in the car. Amir's mother has been convicted of being involved in the toddler's disappearance, but the boy has yet to be found.
Six-year-old Morgan Nick went missing in June 1995 after playing with other children after a Little League game in Alma, Arkansas. Police believe Morgan was abducted by a stranger. 
When high school junior Kara Kopetsky didn't come home from school one day in May 2007, her parents filed a missing person report. Police in Belton, Missouri, told them they believed she was a runaway and would return in a few days. Shortly before she vanished, she told her parents her former boyfriend was stalking her. 
Seven-year-old Kyron Horman was last seen in June 2010 at his Portland, Oregon, elementary school after attending a science fair. While there has been intense speculation surrounding the boy's stepmother, who told police she dropped him off, no charges have been filed in the case and no one has officially been named a suspect. 
Lisa Irwin's father arrived at their Kansas City home from work to find the door unlocked, the lights on and a window tampered with. Lisa's mother said she last saw the 11-month-old the evening before. Dozens of investigators, including police and FBI personnel, have conducted numerous searches for the missing girl but have come up empty. 
Six-year-old Isabel Celis's parents reported her missing in April 2012, telling Tucson, Arizona, police that she vanished from her room in the middle of the night. There are no suspects in her disappearance. 
Jacob Wetterling was abducted at gunpoint in October 1989 at age 11 near his home in St. Joseph, Minnesota, near St. Cloud. His mother, holding a photo of her son, remains hopeful that he will be found alive. 
Christopher Abeyta was only 7 months old when he was taken from his crib in 1986. This year, his family announced a $100,000 reward for help in finding Christopher, who would be 27 today and may look like the image rendering on the right. 
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The faces of some of America's missing "We think that he's capable of anything at this point," he said.
Based on what the sheriff's investigators have seen, there is evidence that the fire and kidnapping of Hannah was a "very well planned event," Fraser said.
Manhunt continues
On Friday, Idaho joined the list of states that have issued an Amber Alert for the missing teen and the suspected child kidnapper.
Four other states -- California, Oregon, Washington and Nevada -- had previously issued Amber Alerts.
DiMaggio is a camper, so it is possible that he is hunkered down somewhere in a rural area, the San Diego Sheriff's Department said.
Why more Amber alerts will be waking you up
The manhunt has been ongoing all week, and authorities have been counting on the public for clues that may lead them to DiMaggio.
"We've got law enforcement agencies across the country looking for them and following up on tips that are being called in," San Diego County Sheriff's Department Lt. Glenn Giannantonio told CNN on Thursday. "We've received numerous tips, I'd say probably well over 100, possibly hundreds of tips from across the country. Every tip that can be followed up on has been followed up on or is currently being followed up on."
It is also possible DiMaggio has abandoned his car and left it rigged with explosives, sheriff's spokeswoman Jan Caldwell said Thursday.
Fraser didn't elaborate on Friday, except to say that evidence at the burned house indicates that there are explosives.
Father of missing children pleads for daughter's release
Suspect is family friend
DiMaggio was described as being so close to the family whose life he allegedly turned upside down that he was considered part of it.
He came into the lives of Brett and Christina Anderson months before their daughter, Hannah, was born.
"He basically became part of our family," Brett Anderson told CNN's Chris Cuomo on Thursday.
DiMaggio was such good friends with the family that Anderson said he can't reconcile the man he knows with the crimes he is suspected of.
"I have been through every scenario in my brain," Anderson said. "There was nothing ever to show any indication of this."
DiMaggio joined the family on campouts and was always friendly toward them, he said.
"I can't fathom what happened in Jim's head. He obviously just lost it," Anderson said.
"You've taken everything," the father pleaded to DiMaggio in the interview. "The damage is done. Just let my daughter go, Let her go home safe, let her be with me and try to mend things from there."
Some witnesses have told investigators that DiMaggio had a crush on Hannah, but Brett Anderson has said the family had no knowledge of that.
Fraser said that they are looking into whether the suspect possibly had an "undue infatuation" with the teen.
Awaiting ID of remains
The remains of Christina Anderson, of Lakeside, California, were found while firefighters extinguished the blaze that broke out at DiMaggio's home in the enclave of Boulevard around 8 p.m. Sunday.
In addition to her body, charred remains consistent with those of an 8-year-old child were found, authorities said. The remains were so badly burned that carrying out a DNA test is proving difficult.
It is possible that the remains are those of Ethan, but until there is a positive identification, the sheriff's office is treating him as a missing person.
CNN's Paul Vercammen, Miguel Marquez and HLN's Katherine Cavazini contributed to this report.
