BOISE, Idaho — Wednesday marks the fourth year without answers in the case of an Idaho boy reported missing in Lemhi County. 

Two-year-old DeOrr Kunz Jr.'s parents called police on July 10, 2015, telling dispatchers their toddler had vanished from a campground near Leadore. Despite extensive searches of the area and prolonged investigations by county law enforcement, the FBI and multiple private investigators, the boy was never seen again.

Previous Lemhi County Sheriff Lynn Bowerman told KTVB he believes that DeOrr is dead, but no one has ever been arrested or charged in the case. Much of the speculation has been aimed at the boy's parents, his great-grandfather and a family friend, all of whom accompanied him on the trip where he was reported missing. 

MORE: 'We're not done by any means:' Campground linked to missing DeOrr Kunz Jr. reopens after search

All four have insisted they had nothing to do with DeOrr's disappearance, and did not harm him. 

Recently, authorities launched another search, closing down the Timber Creek Campground for a weekend. 

PREVIOUSMother of missing toddler: 'Any answers are better than what we have now' 

Private investigator David Marshburn told KTVB the closure came after his cadaver dogs alerted on the scent of human remains within a specific area of the campsite. Marshburn was not involved in the ensuing search, and county authorities have declined to say if they turned up anything connected to the missing toddler case. The campground reopened to the public July 1. 

MOREGone without a trace: What happened to DeOrr Kunz?  

Lemhi County Sheriff Steve Penner told KTVB the investigation is ongoing.