By REBECCA BOONE and ELLIOT SPAGAT FILE – This combination of undated file photos provided by the San Diego Sheriff’s Department shows James Lee DiMaggio, 40, left, and Hannah Anderson, 16. A massive search entered a seventh day Saturday, Aug. 10, 2013, for DiMaggio, suspected of abducting 16-year-old family friend Hannah. DiMaggio is suspected of killing Hannah’s mother Christina Anderson, 44, and her 8-year-old brother Ethan Anderson, whose bodies were found Sunday night in DiMaggio’s burning house in California near the Mexico border. (AP Photo/San Diego Sheriff’s Department, File) CASCADE, Idaho (AP) — The search for 16-year-old Hanna Anderson and her suspected abductor, 40-year-old James Lee DiMaggio, has spanned three states and thousands of miles. But now that law enforcement officers are at their closest yet to finding the pair, they face perhaps the most challenging search area of all. The Frank Church River of No Return Wilderness is the largest roadless area in the Lower 48 states, sprawling across central Idaho and reaching north to the Montana border. To call the mountainous terrain rugged is an understatement. “It’s called the River of No Return for a reason,” said Mike Medberry, a 57-year-old writer and backpacking enthusiast who hiked in the area three summers ago. “This is country that is really up and down. It’s harsh and rugged, with steep terrain, lots of downed logs and thick brush.” DiMaggio is suspected of killing Hannah’s mother Christina Anderson, 44, and her 8-year-old brother Ethan Anderson, whose bodies were found Sunday night in DiMaggio’s burning house in California near the Mexico border. Ethan Anderson’s remains were not positively identified until Friday night, when the San Diego County Sheriff’s Department said its crime lab had used DNA to determine Ethan’s identity. An Amber Alert was initially issued for both children. DiMaggio’s car was found Friday morning about 40 miles east of the tiny town of Cascade, parked where the dirt road ends and the Sand Creek trailhead enters the wilderness area. The discovery came about two days after a horseback rider reported seeing the man and girl hiking in the area. Ada County Sheriff’s department spokeswoman Andrea Dearden, who is helping the Valley County sheriff’s department handle the case, said the rider didn’t realize the pair were being sought until he got home and recognized the pair in news reports. There have been no other reported sightings of the pair since Wednesday, but the discovery launched a massive search in the southwest corner of The Frank Church-River of No Return Wilderness. More than 100 people were searching on foot and on horseback or were on their way to join the search of an area that Ada County sheriff’s spokesman Patrick Orr described Friday evening as covering 320 square miles. “A missing hiker in the foothills is different than searching for a murder suspect, and the risk of that alone comes as a challenge to the search teams,” Dearden said. “When you have a square mile on flatter land, or even water, you can create a grid and literally search every inch. But when you have terrain like this, and this much land, you just can’t do that.” The search area is bisected by the Middle Fork the Salmon River, a wild waterway that winds through steep canyons and dense forests. The river is extremely popular for recreationists and floaters, some of whom will pay up to $2,000 for multi-day, guided trips down the river. But away from the river, it’s easy to disappear, said Jared Hopkinson, the owner of Rocky Mountain River Tours in Stanley, Idaho. Hopkinson said a backpacker can hike for days without seeing a soul — not a fellow camper, not a rafter, not one of the maybe-mythical Idaho hermits that river guides are fond of telling stories about. “If you wanted to go days without being seen, that’s the place to do it,” said Hopkinson. “There’s a few river lodges that are accessible by fixed wing plane and raft, but other than that it is untouched by mankind, the same way it was when there were dinosaurs.” This time of year, the temperatures generally dip into the 40s at night and reach into the 80s during the day, said Rob Terry, the mayor of Cascade and a backcountry pilot who volunteers with the fire department, often helping injured recreationists trapped in the wilderness area. “Fortunately, it’s summer and not winter, and fortunately they’re in an area with water,” Terry said. “Just a couple weeks ago there was somebody who was lost while climbing in that area, probably within 10 miles of where he is now.” Rescue crews were able to locate the climber and bring him to safety — but that search was simplified by the fact that the climber stayed in one place and waited for help, he said. “There’s the key. If he doesn’t want to be found, he just drops off the side of the trail,” Terry said. “It would be very easy if you want to get lost. But unless he was really planning some back country type thing, he may not have carried a lot of food. And while there’s water, it’s suspect — it has giardia and stuff in it. Any knowledgeable backpacker would carry a water filtration system with them.” That’s also assuming DiMaggio stayed within the wilderness area. Dearden said officials don’t know if DiMaggio had rafting equipment available or if he could have left the wilderness by hiking out another trailhead. No cars have been reported stolen or missing in the area, but some rafters and campers may leave a vehicle parked for a week or more, so a stolen vehicle wouldn’t necessarily be discovered right away. Police have set up check points in the area where the car was found and near other nearby trailheads. Law enforcement officials in San Diego have noted that DiMaggio bought camping gear a few weeks ago. DiMaggio was close to the family. Brett Anderson has described him as a best friend and said his children thought of him as an uncle. Authorities have said DiMaggio had an “unusual infatuation” with the 16-year-old, although the father said he never saw any strange behavior. If he had, he said, “we would have quashed that relationship in an instant.” ___ Spagat reported from San Diego. AP writers Bob Jablon and John Antczak contributed to this report from Los Angeles. AP writer Todd Dvorak contributed from Boise.