Tune into "Nancy Grace" tonight for the latest on the disappearance of two toddlers from a camping area in Arizona. "Nancy Grace," Wednesday at 8 p.m. ET on HLN.
(CNN) -- A second 2-year-old boy has gone missing in 10 days from Yavapai County, Arizona, authorities said Tuesday as they announced a major search effort under way for the toddler, identified as Emmett Trapp.
Emmett's disappearance is believed to be unrelated to the case of Sylar Newton, another 2-year-old who was reported missing July 25 from a camping site in Rimrock, Yavapai County Sheriff's Office spokesman Dwight D'Evelyn said.
Sylar's disappearance is now being investigated as a criminal case, authorities said Monday.
Emmett was reported missing by his mother at 8 p.m. Monday, the sheriff's office said in a news release.
The mother told authorities that she and her four children were at their home in the Dewey-Humboldt area, about 80 miles north of Phoenix. When the mother awoke from a nap Monday evening, Emmett -- last seen wearing a pajama top and a diaper -- was missing.
The family dog had also apparently wandered off with Emmett but returned when called. The mother told police she searched around the home and immediate area without success.
Authorities have conducted aerial as well as ground searches for the boy, according to the sheriff's office.
"There is no evidence of foul play associated with the missing child as of now," the news release said.
Meanwhile, D'Evelyn said Tuesday that the investigation into Sylar's disappearance is ongoing.
Sylar was last seen shortly after midnight July 24, sleeping in a tent with his custodial family at the Beaver Creek Campgrounds. About 1:45 a.m. July 25, the family noticed that he was missing from his sleeping bag.
"The sheriff's office believes Sylar did not wander from the campground, and he is presumably dead," Yavapai County Sheriff Steve Waugh said Monday. "The search effort is now in a recovery mode and the investigation has become criminal in nature."
Waugh said investigators have spent three days searching more than 200 tons of garbage in a nearby landfill "to try to determine if in fact the boy's body was there."
Sylar was camping with Christina Priem and her children when he disappeared. Priem has said she was in the process of adopting the boy from his biological mother.
D'Evelyn said last week 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."
About 25 other people were at the campgrounds the night of Sylar's disappearance, all of whom have cooperated with investigators, according to the sheriff's office.