(CNN) -- The search for a missing 7-year-old Oregon boy is now in its fifth day.
Police said they are not ready to call Kyron Horman's disappearance a criminal investigation yet, while the boy's parents have indicated they will release a statement to the public sometime Wednesday.
"We're not prepared to call it a criminal investigation at this point," Captain Jason Gates of the Multnomah County Sheriff's Office told reporters Tuesday, "But we are certainly prepared to call it a missing endangered child investigation."
He also narrowed the scope of the incident.
"What I can tell you is that we have no reason to believe that this is anything other than an isolated case," Gates said.
Kyron was reported missing by his stepmother Friday afternoon after he did not return home from school, authorities said.
According to investigators, Kyron's stepmother said she last saw him Friday morning walking down a hallway towards his second-grade classroom at Skyline Elementary School.
The school was holding a science fair at the time, officials said.
"We can tell you that we have completed 99 percent of the interviews with the children at Skyline Elementary School," Gates said. "We've also completed the majority of interviews with the staff and parents at Skyline."
The sheriff's office said no one at the school saw Kyron after 8:45 a.m. Friday and that Kyron never made it to his classroom.
Authorities continue to pursue hundreds of tips, most of them from Oregon and Washington.
"The leads that are being provided would not suggest that it would be a national search at this point," Gates said.
"We don't have enough information to satisfy the criteria to complete an Amber Alert or issue an Amber Alert," Gates explained. "Amber Alerts are designed to find children very quickly when we have specific information."
Anyone with information on Kyron Horman's whereabouts is asked to call the Multnomah County Sheriff's Office at 503-261-2847