Detectives initially believed the boy, a computer whiz, may have met someone over the Internet.
On Sunday, homicide detectives returned to the neighborhood where the boy, then 14, was last seen. They brought along a backhoe, radar equipment and specially-trained dogs to search for signs of Shelby, neighbors said.
Detectives were working on an old case, sheriff's spokeswoman Rebecca Hover said. She would not provide any other details about Sunday's search.
Shelby was last seen late July 2004.
He had been living with his great-grandmother that summer. The boy cared for her during the day while her son was at work, according to a search warrant filed October 2004. His grandparents reported him missing when they returned from an out-of-town trip. Shelby was gone and so was his laptop computer.
Investigators on Sunday spent several hours digging up the yard around the house where Shelby stayed with his great-grandmother. She has since died and the house has been vacant, tenant Alan Jacobson said.
Jacobson parked his motor home on the property about three months ago. He'd been asked to keep an eye on the house because of several burglaries in the area, he said. The property has been sold, Jacobson said.
"I think they wanted to take one more look before it is developed," he said.
He hadn't heard about Shelby's disappearance until detectives handed him a search warrant that said they had a court's permission to search for evidence of a possible murder, he said. They were looking for clothing, Shelby's eyeglasses and possible human remains, according to the document, which Jacobson carried folded up in a back pocket on Tuesday.
Detectives dug up the back yard and drained the septic tank, he said.
He doesn't know what, if anything, they found on the property in Machias.
Detectives also searched two other properties about a mile away on 135th Avenue SE. Investigators had gone to those homes in 2004, when they questioned a man about Shelby's disappearance. The man was a friend of Shelby's mother and the teen sometimes stayed with him, according to the 2004 search warrant.
A witness in 2004 told detectives that he encountered the boy at the home -- the last anyone apparently reported seeing the teen, according to the 2004 search warrant.
The boy's motorized scooter was later found in the yard.
The 2004 search warrant was for Shelby's e-mail accounts and the investigation then was focusing on the possibility that the boy had been kidnapped. He'd been known to frequent Internet chat rooms and detectives were trying to determine if he'd met someone over the Internet.
The teen's computer records were seized but police haven't shared what they found.
Reporter Diana Hefley: 425-339-3463 or email@example.com.
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