Riverside County Sheriff's Deputy Albert Martinez said investigators had ruled out the father of Terry Dewayne Smith Jr. in the disappearance of the Menifee boy, who lives with his mother and two siblings, The (Riverside) Press-Enterprise reported.
"To our knowledge there's no contact between him and the child," Martinez said.
Authorities also had checked out known sex offenders in the area and came away without a suspect, the deputy said.
"Those were definitely areas of concern for us," he said.
More than 100 law enforcement personnel and volunteers combed the hilly area Monday in temperatures that rose above the 100-degree mark, the newspaper said.
"The concern is how easy it is to dehydrate," Martinez said.
The deputy said the 4-foot-8, 76-pound boy was babysat by his teenage brother while their mother went out the previous evening. They discovered him missing about 10:30 a.m. Sunday, Martinez said.
"When they woke up in the morning he wasn't there," Martinez said.
Terry, whose nickname is "JuJu," has sandy blond hair and blue eyes, and was last seen wearing blue basketball shorts, the Riverside County Sheriff's Department said in a news release. He also responds to the nickname "JuJu."