Sheriff Waugh said, "A 2-year-old has no survival skills. When they are hungry, they cry. When their diaper is dirty, they cry. It's a rugged area and we thought we would hear him crying for those needs. That did not happen."
The family has been cooperative during interviews, Waugh said, but officials have yet to complete analyzing polygraph interviews. Christina Priem is adopting the child. She was with her mother, and three other children.
Boelts would not identify specific persons of interest: "We have not ruled anyone in or out."
The Sheriff's Office has canvassed sex offenders in the Verde Valley and combed through 200 tons of garbage taken from the campground at the Grey Wolf landfill.
There still are video camera films to examine from surrounding stores and businesses.
Behavior analysts from Utah and experts from the National Center for Missing and Exploited Children have advised detectives on a child's movements, which would have been limited to less than a mile radius around the camp.
Boelts said the agency has received numerous tips. "We have the usual psychic tips. We have had tips from the National Center, that I would rather not go into. We have also had tips reference Internet activity."
The Child Abduction Rapid Deployment Team with manpower from Boston, San Francisco, New Jersey and Phoenix have assisted in the search. Horses were brought from Coconino County. Search crews had access to sonar equipment from Pima County. They checked water pools, used cameras in wells and even checked vault toilets.
Newnum said to date, 380 search personnel have invested 4,109 hours over the past eight days and searched 8.5 square miles, working with lines of 15 people one arm length apart. If there were clues, "we would not have missed them," he said.
"It's heartbreaking," Sgt. Newnum said. Many of the searchers have children as well. "We fell in love with Sylar even though we never met him.
"I have four kids at home and you go home and hug your kids. Nobody wanted to stop."
Even so, the search and the investigation continued as reporters were briefed. The campground has now reopened, with posters everywhere asking visitors to help find the missing 2-year-old from Flagstaff.