CARLSBAD, Calif. -- Detectives investigating a North County teenager's disappearance in Joshua Tree National Park searched the home of a friend who accompanied the boy on the outing.

MISSING HIKER Search For Missing Hiker Takes Disturbing Turn Police Search Friend Of Missing Hiker's Home Community Holds Vigil Search For Missing Carlsbad Hiker

About a half-dozen investigators from the Central Homicide unit of the Riverside County's Sheriff's department spent six hours Thursday at the home of one of Sears' friends in Carlsbad in connection with the disappearance of Eric Sears, also 17, 10News reported.

The friend's identity cannot be identified because he is a juvenile.

Sears went missing July 15 while he and his friend were staying at the Jumbo Rocks campground at Joshua Tree.

Riverside County authorities conceded they believe Eric may have fallen victim to some sort of crime, as opposed to merely getting lost in the wilderness.

"We're trying to find any evidence of value out here," Sgt. Earl Quinata, a Riverside County sheriff's department spokesman, said.

Quinata said there was "probable cause" to search the home based on interviews with more than 30 people during the past week. He said the boy is not a suspect.

"This is just one of the many avenues we're exploring," Quinata said, adding that the friend and his family were "cooperating completely."

Eric's parents have clung to the hope that he will turn up safe, and conducted their own search Thursday.

The National Park Service reopened the Jumbo Rocks campground Thursday, which had been closed since Friday.