(CNN) -- Authorities in Rimrock, Arizona, were searching Monday for a 2-year-old boy who went missing over the weekend while camping with a family that was preparing to adopt him, a spokesman for the Yavapai County Sheriff's Office said.
Syler Newton was last seen shortly after midnight Saturday, sleeping in a tent with the family at the Beaver Creek Campgrounds. About 1:45 a.m. Sunday, the family noticed that he was missing from his sleeping bag.
About 50 people, along with bloodhounds and tracking teams, have joined in the search for Syler, who was wearing only a diaper when he disappeared, according to Yavapai County Sheriff's spokesman Dwight D'Evelyn.
"Right now, there's no indication he was taken from the site," D'Evelyn said Monday evening, adding that investigators are "looking at every possible reason that Syler is missing."
D'Evelyn said bloodhounds normally used by the Department of Corrections to help find escaped felons picked up Syler's scent around the campsite Monday, but failed to detect his scent outside a particular radius.
Angela Godinez, the sister of the woman preparing to adopt Syler, told CNN affiliate KPHO on Monday that the family is "preparing for the worst."
"We're all really, really scared, because he's only 20 pounds," she said. "He could have been carried away easily. He could have froze last night or gotten heatstroke today."
"We don't know what's going on, and there's a lot of possibilities," she added, her voice breaking.
She said she fears that Syler is "somewhere along the water." The campgrounds sit on the banks of the Wet Beaver Creek.
"That's why I'm really, really scared, because he's always loved the water," she said.
Godinez said her sister, identified by police as 36-year-old Christina Priem, is in the process of finalizing an adoption agreement with Syler's biological mother.
D'Evelyn said the Department of Child Services was involved in the investigation and was working to corroborate the adoption story.
FBI authorities were able to make contact with the Syler's biological mother Monday, but D'Evelyn did not know the outcome of that conversation.
"Until we speak to the biological mother, we just don't know the full story," D'Evelyn said.
He later added that "there's no evidence" that the planned adoption played a role in his disappearance, "but until we've exhausted every lead, all possibilities are being investigated."