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The father of missing Tucson, Ariz., girl Isabel Celis sounds calm as he describes finding that the 6-year-old has disappeared from her bed and tells police he thinks she was abducted in the recordings of two 911 calls released today by police.

"I want to report a missing person," Sergio Celis says on one of the two recordings, made the morning of April 21. "My little girl, who is 6 years old - I believe she was abducted from our house."

The second recording is of a call featuring Isabel's 14-year-old brother, Sergio, who later gives the phone to his mother after she returns home from work. Both the boy and his mother are frantic, though the woman seems to control herself when she is asked for specific information about the girl's height and weight, what she was wearing, and her hair and eyes.

Police today also discussed the decision to bar Sergio Celis from contact with his two sons, though they declined to provide any specifics about the reason for the decision. They said the move should not be interpreted as an indication that Sergio Celis is a suspect in his daughter's disappearance.

"A voluntary agreement was reached between Child Protective Services and the parents to restrict access or, voluntarily, for Sergio to give some space and distance away from the two older children," Tucson Police Chief Roberto Villasenor said.

"This doesn't mean that we have settled on a path with this investigation," he said.

He added that investigators are looking at all possibilities.

"Probably, [there are] about 12 to 15 detectives that are assigned to follow external viewpoints on this investigation, the possibility of a stranger abduction or something of that like," he said. "And then, we have probably four detectives or so that are following the possibility of inside-the-family involvement."

Isabel Celis was reported missing by her father around 8 a.m. April 21 after her mother left for work and her father went to wake her up.

The girl was not in her room, and a bedroom window was opened with the screen removed, police said.

The little girl was last seen around 11 p.m. April 20, when she was put to bed.

After Isabel was reported missing, police interviewed 15 registered sex offenders in the neighborhood.

Police have searched homes in the family's neighborhood, dug through a nearby landfill and searched waterways and drainage systems in Tucson. More than 1,000 tips have poured in regarding the 6-year-old's disappearance, police said.

Isabel's parents made several public, emotional pleas for the safe return of their daughter in the days after her disappearance.