A private investigator seeking answers about what happened to a 2-year-old boy who went missing in Idaho last summer said Friday the disappearance had been moved to cold case status.

"We have no further credible leads that we can investigate to move the case forward," investigator Phillip Klein said in a statement.

The family of DeOrr Kunz Jr. contends the boy disappeared during a camping trip near Leadore in July 2015. Extensive searches of the campground, forest and nearby reservoir have yielded nothing.

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In the absence of either a body or a sighting of the child alive, suspicion has landed squarely on the shoulders of DeOrr Jr.'s parents, Jessica Mitchell and DeOrr Kunz Sr. The Lemhi County Sheriff's Office has officially named them suspects in the disappearance. Sheriff Lynn Bowerman told KTVB he believes the case is a homicide and that DeOrr Jr. was never at the campground.

The sheriff's sentiments are shared by Klein, who has previously told KTVB he thinks DeOrr Jr. was killed by his parents, either intentionally or by accident. DeOrr Jr.'s parents says they plan to sue Klein and his firm.

In meantime, DeOrr's grandmother denies her daughter hurt the boy.

"Where is the body, where's blood or where's physical evidence that would show that there was a homicide?" Trina Bates Clegg said.

RELATED: Lemhi County sheriff: DeOrr's case 'has to be a homicide'

Klein said he has poured more than 1,000 hours and $15,000 into the case, not counting money donated to help in the search.

"We want to say that we firmly believe and have zero indication(s) that an animal took the child and we have zero indications of any abduction of the child," Klein said in his statement.

Klein said moving the inquiry to a cold case does not mean he is abandoning the investigation. Instead, investigators will start over and review all the evidence again, looking for any clues they may have missed. Klein's team will also explore what he has termed "secondary areas" in the Leadore area.

"'We are broadening our area in Leadore," Klein said.

READ: Lemhi County Sheriff: Campground closed off to search for DeOrr Kunz Jr.

"On a more personal note, our team would like to say thank you for the warm welcome the citizens of Idaho have given us," the statement reads. "We are proud to be part of a team of people that have one common goal - to bring DeOrr Kunz Jr. home to his resting place. We want you to know that we have always had hope that we were wrong - that we missed something - or that maybe that there was a chance of some type of abduction. However, we simply do not see any evidence that leads us to that conclusion."

Klein said he has "been met with nothing but story after story that changes" from the people - Mitchell, Kunz Sr. and family friend Isaac Reinwald - who were at the campsite when the boy disappeared. He said he is frustrated, and convinced that the trio has the answer.

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"Simply put - just tell the truth," he said in the statement." Stop making up stories and stop misleading law enforcement and our firm. As well, we call on those close to the suspects to stop enabling them and confront them with their stories."

Clegg says she's spoken to her daughter a number of times about that day and says she has gotten a few different stories. But she says that's to be expected.

"You tell it, you try to write it down and then in a couple of days you're like 'I remember that this happened.' Is it that the stories change or is it that something comes to mind that they left out in the beginning? That's my thing," Clegg said.

Lemhi County Sheriff's Office Chief Deputy Steve Penner said Friday their investigation is still active. The sheriff's investigation has always been separate from that of Klein's firm, he said, and the private investigator's decision to label it a cold case will not influence the work of law enforcement.

Anyone with information about the DeOrr Jr.'s whereabouts is urged to contact law enforcement. To read Klein's full statement, click here.