For the past 10 days, Lemhi County Sheriff Lynn Bowerman and his deputies have scoured the rugged terrain surrounding a remote Idaho campsite for a missing 2 year-old boy -- using sonar imaging equipment to probe a nearby reservoir and searching a wolf den for any trace of the child.

As of Monday, authorities said they have no clue where Deorr Kunz could be, after the Idaho Falls toddler disappeared July 10 from a campsite near the Timber Creek Reservoir in Leodore where he was staying with his parents, great-grandfather and another adult.

"We've literally torn that country apart and found absolutely not one clue," Bowerman told FoxNews.com.

"We conducted an exhaustive search of the area, which included eight agencies, multiple dog search groups and well over 100 people," he said.

"We've literally torn that country apart and found absolutely not one clue."

- Lemhi County Sheriff Lynn Bowerman

At 2:30 p.m. on July 10, the child's 25-year-old mother, Jessica Mitchell, called 911 from the campsite to report her son missing. Mitchell and the boy's father, Deorr Kunz Sr., said they left their son with his great-grandfather while they went off to explore. The great-grandfather believed the boy was with his parents, according to police.

What happened during the 20 to 45 minutes the child was alone is a mystery to authorities, said Bowerman, who noted "all possibilities" are being investigated.

The family's campsite sat approximately 40 yards from a fast-moving creek -- four to six feet in width and about a foot deep -- that spills into the Timber Creek Reservoir, a half mile from where the toddler was last seen.

Cadaver dogs led law enforcement directly to the reservoir but Bowerman said unrelated cremated remains dumped into the water during the search likely prompted the canines' interest. A search of the reservoir using advanced sonar equipment yielded nothing, he said. 

Over the weekend, the sheriff and his deputies carefully examined a nearby wolf den but found not a single clue -- no remnant of clothing or sign the boy had been dragged from the campsite. 

"We've got a pack of wolves in there -- about 15 of them," Bowerman said. "We actually chased one out the day before yesterday." 

The boy's parents, meanwhile, have volunteered to take polygraph tests after being interviewed and having their vehicles examined by police. The two have said they believe their child was abducted.

"I don't look at them as suspects at this point in time," the sheriff noted. "They want to believe he's abducted because that would make him still alive."

Bowerman, however, said he's not convinced of an abduction, noting that no other campers were seen or heard in the area at the time of the disappearance. He also described the terrain as "steep and rugged" and said vehicles can reach the site but "the road is extremely rough."

"We don't have any evidence that somebody kidnapped this child," he said.

Still, the Lemhi County Sheriff's department has received tips from Canada to southern California to New York reporting a possible sighting of the child.

While stranger abductions are rare, such was likely the case for Janet Castrejon, who disappeared in June while camping with her parents in the Chiricahua Mountains in southeast Arizona, some 50 to 60 miles from the Mexican border. After an exhaustive search of the area, police said they believe 44-year-old Castrejon -- who has the mental capacity of a child -- was taken by vehicle from the mountain.

The Castrejons arrived at Rustler Park campground at around 2 p.m. on June 19 to enjoy a Father's Day weekend in the mountains. At 6:30 p.m., while still light out, Castrejon and her mother left the family's RV to deposit a campground fee in the designated self-pay station -- a short walk along a dirt road down a hill and around a bend.

After the fee was deposited, Castrejon's mother walked a little further downhill from the fee station to use a restroom, while the woman headed uphill toward the campsite, according to the woman's brother, Fabian Castrejon. When the mother exited the restroom approximately three to five minutes later, her daughter was nowhere to be found. Bloodhounds followed Janet Castrejon's scent along the road before the trail went cold, her brother said, suggesting she got into a vehicle.

"She was an easy target," Fabian Castrejon said of his sister, who was left mentally impaired as a teenager after suffering a traumatic brain injury in a car accident. "She behaved like a child."

"The consensus is that she was abducted," he said. "The authorities just flat out said she's not up there."

Cristina Corbin is a reporter for FoxNews.com. Follow her on Twitter @CristinaCorbin.